【小白求助】逻辑两道

门外汉ing~请求指点，领入门中！谢谢！
GWD1-Q3:
A product that represents a clear technological advance over competing products can generally command a high price.  Because technological advances tend to be quickly surpassed and companies who want to make large profits while they still can, many companies charge the greatest price the market will bear when they have such a product.  But large profits on the mew product will give competitors a strong incentive to quickly match the mew product’s capabilities.  Consequently, the strategy to maximize overall profit from a new product is to charge less than the greatest possible price.
In the argument above, the two portions in boldface play which of the following roles?

A. The first is an assumption that forms the basis for a course of action that the argument criticizes; the second presents the course of action endorsed by the argument.
B. The first is a consideration raised to explain the appeal of a certain strategy; the second is a consideration raised to call into question the wisdom of adopting that strategy.
C. The first is an assumption that has been used to justify a certain strategy; the second is a consideration that is used to cast doubt on that assumption.
D. The first is a consideration raised in support of a strategy the argument endorses; the second presents grounds in support of that consideration.
E. The first is a consideration raised to show that adopting a certain strategy is unlikely to achieve the intended effect; the second is presented to explain the appeal of that strategy.
我选的是D，我现在知道错了，是因为文中没有同意这个策略
但是想知道为什么会是B，有什么标志吗？怎么选到B呢

GWD1-Q13:
In the United States, of the people who moved from one state to another when they retired, the percentage who retired to Florida has decreased by three percentage points over the past ten years.  Since many local businesses in Florida cater to retirees, this decline is likely to have a noticeably negative economic effect on these businesses.
Which of the following, if true, most seriously weakens the argument?

A. Florida attracts more people who move from one state to another when they retire than does any other state.
B. The number of people who move out of Florida to accept employment in other states has increased over the past ten years.
C. There are far more local businesses in Florida that cater to tourists than there are local businesses that cater to retirees.
D. The total number of people who retired and moved to another state for their retirement has increased significantly over the past ten years.
E. The number of people who left Florida when they retired to live in another state was greater last year than it was ten years ago.

这个我选的A，当时在A和D之间犹豫不决，觉得A至少还提到了地名，所以选了，就错了
谢谢解答

第一题的划线部分在哪里？

第二题：

原文大意：

因为——退休旅居F的人数百分比下降

             许多F企业迎合退休人员

所以——影响了F的经济

A只是说F的人数比其他地区多，这并不能肯定F的人数上升。因为，如果总人数下降，那么即使F的人数比其他城市人数多，也不能说F增加了。

D只是说总人数增加，并不必然意味旅居F的人数一定增加

C是说，当地企业的经济增长主要靠旅游者人数，不靠退休人员人数。所以应是正确选项。

I agree with you, Hongweishan. The best choice should be C. Thank you for your reminding.

IMO，C中的选项和原题没有关系，文章的结论是this decline is likely to have a noticeably negative economic effect on these businesses，而these business 是指那些给退休的人提供饮食的商家，所以应该针对在F的退休人数是否真的减少来削弱，而原文提到只是percentage的减少，所以只要能削弱这个就可以了。答案应该是D，他实际在说的是F的实际退休人数可能因为其他地方的人过来而增加