请教NOT +WEAKEN

请哪位前辈结合下面两道题给我讲下 取非削弱，听FF的网络课程没听懂呢。

例5. Statistics over four consecutive years showed that four percent more automobile accidents happened

in California during the week following the switch to daylight saving time and during the week

following the switch back to standard time than occurred the week before each event. These statistics

show that these time changes adversely affect the alertness of California drivers.

  The conclusion in the argument above is based on which of the following assumptions?

(A)   Drivers in California as well as those in the rest of the United States have similar driving patterns.

(B)   The observed increases in accident rates are due almost entirely to an increase in the number of minor accidents.

(C)   Four years is not a sufficiently long period of time over which to judge the phenomenon described.

(D)   There are no other factors such as school vacations or holiday celebrations that cause accident rates to rise during these weeks.

(E)   A time change at any other time of year would not produce a similar increase in accident

 选择D

例6．Although the ratio of physicians to total population is about the same in the United
                State and Canada, the United States has 33 percent more surgeons per capita. Clearly, this is the reason people in the United States undergo 40 percent more operations per capita than do Canadians.

The explanation given above rests on an assumption that

(A)patients in the United States do not have a greater need for surgery than do patients in Canada.

(B)the population of the United States is not larger than that of Canada.

(C)United States patients sometimes travel to Canada for certain kinds of surgery.

(D)general practitioners in the United States do not as a rule examine a patient who is a candidate for surgery before sending the patient to a surgeon.

(E)there are no unnecessary surgical operations performed in Canada.

选择A

多谢。。