占比最大，主要包括增强和削弱两大问法，以下分别举2个列题说明：

Certain groups of Asian snails include both “left-handed” and “right-handed” species, with shells coiling to the left and right, respectively. Some left-handed species have evolved from right-handed ones. Also, researchers found that snail eating snakes in the same habitat have asymmetrical jaws, allowing them to grasp right-handed snail shells more easily. If these snakes ate more right-handed snails over time, this would have given left-handed snails an evolutionary advantage over right-handed snails, with the left-handed snails eventually becoming a new species. Thus, the snakes' asymmetrical jaws probably helped drive the emergence of the left-handed snail species.

Which of the following would, if true, most strengthen the argument that asymmetrical snake jaws helped drive left-handed snail evolution?                                                

A. In one snake species, the snakes with asymmetrical jaws eat snails, while the snakes with symmetrical jaws do not eat snails.

B. Some species of Asian snails contain either all right-handed snails, or all lefthanded snails.

C. Anatomical differences prevent left-handed snails from mating easily with right-handed snails.   

D. Some right-handed snails in this habitat have shells with a very narrow opening that helps prevent snakes from extracting the snails from inside their shells.

E. Experiments show that the snail-eating snakes in this habitat fail more often in trying to eat left-handed snails than in trying to eat right-handed snails.

【题目解析】

逻辑链：蛇更容易吃右撇子蜗牛---最后左撇子蜗牛会成为新物种。问增强

A.在一种蛇中，嘴不对称的蛇吃蜗牛，而嘴对称的蛇不吃蜗牛。讨论不同种类蛇的吃食习惯，无关

B.一些蜗牛包括左右撇子。重复原文已知

C.交配问题。无关

D.解释蛇不容易吃右撇子的原因。攻击并否定前提

E.实验表明吃蜗牛的蛇在尝试吃左撇子蜗牛上比尝试右撇子蜗牛上更容易失败---正确，能够增强。

Mall owner: Our mall's occupancy rate is so low that we are barely making a profit. We cannot raise rents because of an unacceptably high risk of losing established tenants. On the other hand, a mall that is fully occupied costs about as much to run as one in which a rental space here and a rental space there stands empty. Clearly, therefore, to increase profits we must sign up new tenants.

Which of the following, if true, most seriously weakens the argument?

A. The mall's operating costs could be cut by consolidating currently rented spaces in such a way that an entire wing of the mall could be closed up.

B. The mall is located in a geographic area in which costs incurred for air-conditioning in the hot summers exceed those incurred for heating in the mid winters by a wide margin.

C. The mall's occupancy rate, though relatively low, has been relatively stable for several years.

D. The mall lost tenants as a result of each of the two major rent increases that have occurred there.

E. None of the mall's established tenants is likely to need additional floor space there in the foreseeable future.

【题目解析】 

逻辑链:

to increase profits ---- must sign up new tenants.

A 仓库的运营成本可以靠关掉整个侧翼的仓库来压缩；他因削弱，压缩成本（他因）以提高利润，正确

B 仓库所在地区夏天空调成本超过冬天制热成本很多；谈夏冬代价，无关比较。

C 仓库的使用率虽然低但很稳定；与利润无关，排除。

D 两次租金上调损失了大量客户；谈损失客户的原因，无关。

E 现在的租客以后不太可能扩大面积；租客的主观表达，无关。