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问题 单项选择题

近现代以来，科学技术的进步改变了人们的生活质量和生活方式。以下科技成果中属于第二次科技革命的是（）

①汽船

②摄影机

③汽车

④飞机

⑤计算机

⑥核电站

A.①②③

B.②③④

C.②⑤⑥

D.③④⑥

答案

参考答案：B

选择题

不要随地吐痰的主要原因是( )。

A．痰中含有大量细菌

B．痰中含有大量的病菌

C．气管内分泌的黏液太脏

D．以免污染地面
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单项选择题

Ants first captured the attention of software engineers in the early 1990s. A single ant cannot do much on its own, but a group of ants (52) can solve complex problems. That inspired people like Marco Dorigo, who is one of the founders of a (53) known as group intelligence.

Ants are good at choosing the shortest possible route between a food (54) and their nest. This reminds us of a classic computational travelling-salesman problem. Given a list of cities and their (55) apart, the salesman must find the shortest route needed to visit each city once. As the number of cities (56) , the problem gets more complicated.Ants solve their own problem using chemical signals called pheromones (信息素), when an ant finds food, she takes it back to the nest, (57) a pheromone trail that will attract others. The more ants that (58) the trail, the per it becomes. (59) , the pheromones evaporate (挥发) quickly, so once all the food has been collected, the trail soon goes cold. This rapid evaporation means long trails are less (60) than short ones, all else being equal. Pheromones thus turn the (61) intelligence of the individual ants into something more powerful.

59().

A. Therefore

B. Furthermore

C. Then

D. However
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