Directions: There are five reading Passages in this part. Each passage is followed by five questions. For each question there are four suggested answers marked A, B, C and D. Choose one best answer and blacken the corresponding letter on ANSWER SHEET I.Passage OneSince the early 1980s, scientists have revealed some 40 human genes involved in cancer. These genes are essential for normal growth, but can be subverted to cause a tumor.Dr. Jorge Yunis of the University of Minnesota Medical School in Minneapolis has found that 70 percent of oncogenes, or cancer-causing genes, are located near inherited weak points on chromosomes(染色体). Varying from individual to individual, vulnerable to chemical carcinogens(致癌剂) ,X rays and other cancer-inducing agents."If a chromosome snaps apart in the immediate vicinity of an oncogene," says Yunis, "normal genetic control mechanisms could break down and the stage would be set for the formation of cancer." Younis hag shown that such a sequence occurs at the beginning of numerous leukemias (白血病), lymphomas (淋巴瘤) and some tumors of the lung, colon (结肠) and breast.Yunis and Other investigators have found that petroleum-based products--notably pesticides and insecticides--damage specific sites on at least two of the 23 pairs of human chromosomes that carry genetic information. Similarly, tobacco smoke tends to attack a part of another chromosome. Where are most likely to be affected by caner-inducing agents according to the passage()
A. The lung.
B. The colon.
C. The chromosomes.
D. The breast.
患者,女性,30岁,反复发作性喘息3年,近1年来发作频繁,重时端坐呼吸。查体:心率110次/分,呼吸30次/分,双肺可闻广泛性呼气相哮鸣音。血细胞分类示白细胞10.5×109/L,嗜酸性粒细胞占8%。X线胸片示双肺纹理增粗。 诊断支气管哮喘的主要依据是( )
A. 发作重时端坐呼吸
B. 反复发作性喘息3年
C. X线胸片示双肺纹理增粗
D. 发作时双肺可闻及广泛性呼气相哮鸣音
E. 白细胞10.5×109/L,嗜酸性粒细胞占8%