The main idea of this passage is that ______.
A. man's elementary number sense is found in lower species
B. birds have a limited number sense
C. animals cannot count
D. number sense is a primitive form of counting
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Karel Drbal found that his model pyramid could ______.
A. sharpen razorblades
B. stop ice melting
C. produce strange noises
D. make animals become torpid
Why does the author mention the Stanford scientists in the second paragraph
A. To compare hard work done by Roslin Institute to that of the two Stanford scientists.
B. To prove that scientific research can make money be the patent.
C. To suggest that why Geron-Roslin is keen to get its patent.
D. To underline that Geron company is money-oriente
What is David Peakall
A. He is a farmer.
B. He is a scientist of physics.
C. He is a toxicologist.
D. He works at the University of Michigan.
甲氨蝶呤不具有哪项( )。
A. 橙黄色结晶性粉末
B. 为二氢叶酸还原酶抑制药
C. 治疗实体瘤的首选药
D. 用于急性白血病毛膜上皮癌的治疗
E. 在强酸中不稳定，可水解
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