在进行选择育种时，群体遗传变异越大，则所能获得的遗传进展（）。 A.越大 B.无关

在家庭生活中，我们用到了很多的杠杆，请你举出3个例子并说明是属于哪一种杠杆？

杠杆名称一：______，属于 ______杠杆；

杠杆名称二：______，属于 ______杠杆；

杠杆名称三：______，属于 ______杠杆．

下运动神经元损伤的表现为（）

A.随意运动障碍

B.深反射消失

C.浅反射减弱或消失

D.出现病理反射

E.肌张力增高

张某是甲企业的销售人员，随身携带盖有甲企业公章的空白合同书，便于随时对外签约，后来张某因为收取回扣被甲企业除名，但空白合同书未收回，同时也未将张某被开除的消息告知长期客户。某日张某以此合同书与不知情的甲公司的长期客户李某签订了一份商品买卖合同，该合同的效力是( )。

A．不成立
B．有效
C．无效
D．效力待定

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.

61().

A.interrupted 

B.limited 

C.considerable 

D.unreliable