请教几题GWD-TN-24的逻辑

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.
答案D，我选C。如果更多的local businesses是为旅游者服务而不是退休者，那即使退休者减少不是对这个business影响很小吗？答案D过去十年退休者增加就是完全否定了题目的条件而不是削弱啊。

GWD1-Q17:
The spacing of the four holes on a fragment of a bone flute excavated at a Neanderthal campsite is just what is required to play the third through sixth notes of the diatonic scale—the seven-note musical scale used in much of Western music since the Renaissance.  Musicologists therefore hypothesize that the diatonic musical scale was developed and used thousands of years before it was adopted by Western musicians.
Which of the following, if true, most strongly supports the hypothesis?

A. Bone flutes were probably the only musical instrument made by Neanderthals.
B. No musical instrument that is known to have used a diatomic scale is of an earlier date than the flute found at the Neanderthal campsite.
C. The flute was made from a cave-bear bone and the campsite at which the flute fragment was excavated was in a cave that also contained skeletal remains of cave bears.
D. Flutes are the simplest wind instrument that can be constructed to allow playing a diatonic scale.
E. The cave-bear leg bone used to make the Neanderthal flute would have been long enough to make a flute capable of playing a complete diatonic scale.
答案E，我选B。熊的腿骨长短和乐器的发明时间有关系吗？

13. Since the overall retiring population has been increased, the 3% decrease in those who retired to Florida does not matter. The overall retiring people moving to Florida may still increase.

17. B is useless. Even the flute is the earliest instrument, how can you prove the 4-holes fragment of a bone flute is exactly the part of instrument of 7 holes which can play diatonic scale?

E: The flute found in Neandertahl was made by the bear leg. More, the bear leg is long enough to make the flute of 7 holes which can play diatonic scale.

sorry i can't type Chinese in this computer.