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Outline: A. Describe what the girl in the picture is doing; B. Why is the girl in the picture sitting on the baby C. What does the picture imply
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在建立下一个连接请求时，为了实现负载平衡，边界路由器会将虚拟地址映射为一个未曾映射过的内部地址或者是使用次数最少的内部地址。阅读以下说明，回答下面问题。 设有A，B，C，D四台主机都处在同一个物理网络中，A主机的IP地址是202.155.12.112，B主机的IP地址是202.155.12.120，C主机的IP地址是202.155.12.222，D主机的IP地址是202. 155.12.176。共同的子网掩码是255.255.255.224。 【问题3】 若要使主机A，B，C，D在这个网上都能直接相互通信，可采取什么办法
Passage Two Our brains could be hard-wired to be male or female long before we begin to grow testes(丸)or ovaries(卵巢)in the womb. This discovery might explain why some people feel trapped in a body that’s the wrong sex, and could also lead to tests that reveal the true "brain sex" of babies born with ambiguous genitalia(生殖器). Till now, the orthodoxy among developmental biologists has been that embryos develop ovaries and become female unless a gene called SRY on the Y chromosome is switched on. If this gene is active, it makes testes develop instead. This switch is seen as the key event in determining whether a baby is a girl or a boy. Only after the gonads(性腺) form and flood the body with the appropriate hormones, the theory goes, is the sex of our minds and bodies determined. But in a study of mice, a team at the University of California, Los Angeles, has now found that males and females show differences in the expression of no fewer than 50 genes well before SRY switches on. "It’s the first discovery of genes differentially expressed in the brain, "says Eric Vilain, who led the UCLA team. "They may have an impact on the hard-wired development of the brain in terms of sexual differentiation independent of gonadal induction." Vilain is presenting details of seven of the 50 genes to the annual meeting of the American Society of Human Genetics in Baltimore this week. Three of these genes are dominant in females and four are dominant in males. The next step for Vilain and his team will be to show that the genes in question really do influence brain sexuality—and not just in mice. This is likely to be a much tougher proposition than merely showing there are differences in expression. But if the findings are confirmed, they could one day yield blood tests that allow doctors to establish the brain sex of babies born with genitalia that share features of both sexes. At present doctors and parents have to guess which gender to assign for surgical "correction". We can infer from the last paragraph that ______.
/*simple ping program*/ struct sockaddr_in saddr; int rawsock; unsigned short in_cksum(unsigned short*addr, int len) { int sum=0; unsigned short res=0; while(1en＞1){ sum+=*addr++; len-=2; } if(len=1){ *((unsigned char *)(&res))=*((unsigned char *)addr); sum+=res; } sum=(sum＞＞16)+(sam & 0xffff); sum+=(sum＞＞16); res=～sum; return res; } void ping(int signo) { int len; int i; static unsigned short seq=0; char buff[8192]; struct timeval tv; struet icmp*icmph=(struct icmp * )buff; long*data=(long*)icmph→icmp_data; bzero(buff, 8192); gettimeofday(&tv, NULL); icmph→icmp_type=ICMP_ECHO; icmph→icmp_code=0; icmph→icmp_cksum=0; icmph→icmp_id=0; icmph→icmp_seq=0; icmph→icmp_id=getpid()&0xffff; icmph→icmp_seq=seq++; data[0]=tv.tv_sec; data[1]=tv.tv_usec; for(i=8; i＜ ; i++) icmph→icmp_data[i]=(unsigned char)i; icmph→icmp_cksum=in_cksum((unsigned short *)buff, 72); len; sendto(rawsock, buff, 72, 0, &saddr, sizeof(saddr)); alarm(1); } void sigint(int signo) { printf("CATCH SIGINT !!! \n"); close(rawsock); exit(0); } void dumppkt(char*buf, int len) { struct ip*iph=(struct ip*)buf; int i=iph→ip_h1*4; struct icmp*icmph=(struct icmp*)&buf[i]; long*data=(long*)iemph→icmp_data; struct timeval tv; gettimeofday(&tv, NULL); if(icmph→icmp_type! =ICMP_ECHOREPLY) return; if(icmph→icmp_id! =(getpid()&0xffff)) return; printf("From %s:ttl=% d seq=% d time=%.2f ms\n", inet_ntoa(iph→ip_src)，iph→ip_ttl, icmph→icmp_seq, (tv.tv_see-data[0])*1000.0+(tv.tv_usec-data[0])/1000.0)； } int main(int argc, char*argv[]) { int len; stuct timeval now; char recvbuff[8192]; if(1){ printf("%s aaa.bbb.ccc.ddd\n", argv[0]); exit(1); } rawsock=soeket(AF_INET, (2), IPPROTO_ICMP); if(rawsock＜0) { perror("soeket"); exit(1); } bzero ( &saddr, sizeof(saddr)); saddr.sin_family=(3); if( inet_aton( argv[1], &saddr.sin_addr) ＜0) { printf("invalid IP address: %s\n", argv[1]); exit(1); } signal(SICALRM, ping); signal(SICINT, sigint); alarm(1); while (1){ len=read (4), recvbuff, 8192); if( len＜0 && errno=EINTR) continue; else it( len＜0) perror("read"); else if( len＞0) dumppkt(recvbuff, len); } close (5); exit(0); }
Passage One For more than thirty years after astronauts first set foot on the Moon, scientists have been unable to unravel the mystery of where the Earth’s only satellite came from. But now there is direct evidence that the Moon was born after a giant collision between the young Earth and another planet. Previous studies of rocks from the Earth and the Moon have been unable to distinguish between the two, suggesting that they formed from the same material. But this still left room for a number of theories explaining how—for example, that the Moon and Earth formed from the same material at the same time. It was even suggested that the early Earth spun so fast it formed a bulge that eventually broke off to form the Moon. Franck Poitrasson, and his colleagues at the Swiss Federal Institute of Technology have compared Moon rocks with rocks from Earth and discovered a surprising difference. They analysed the weight of the elements present in the rock using a highly accurate form of mass spectroscopy(光谱研究) that involves vaporising a sample by passing it through an argon (氩) flame. Although they appeared very similar in most respects, the Moon rocks had a higher ratio of iron-57 to iron-54 isotopes(同位素)than the Earth rocks. "The only way we could explain this difference is that the Moon and the Earth were partly vaporised during their formation," says Poitrasson. Only the popular "giant planetary impact" theory could generate the temperatures of more than 1700℃ needed to vaporise iron. In this scenario, a Mars-sized planet known as Theia crashed into Earth 50 million years after the birth of the Solar System. This catastrophic collision would have released 100 million times more energy than the impact believed to have wiped out the dinosaurs—enough to melt and vaporise a large portion of the Earth and completely destroy Theia. The debris from the collision would have been thrown into orbit around the Earth and eventually coalesced to form the Moon. When iron is vaporised, the lighter isotopes burn off first. And since the ejected debris that became the Moon would have been more thoroughly vaporised, it would have lost a greater proportion of its lighter iron isotopes than Earth did. This would explain the different ratios that Poitrasson has found. Previous studies could not distinguish between ______.
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