请教PREP里的一些逻辑题~~~

mumuceiber

本人逻辑很不好，一错就错好几个，有几个PREP里的题不太懂，请各位牛牛帮忙解答一下~~~~
1、

An unusually severe winter occurred in Europe after the continent was blanketed by a blue hazeresulting from the eruption of the Laki Volcano in the European republic of Iceland in the summer of 1984.Thus, it is evident that major eruptions cause the atmosphere to become cooler than it would be otherwise

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

(C) A few months after El Chichn's large eruption in April 1982, air temperatures throughout the region remained higher than expected, given the long-term weather trends.

(D) ！The climatic effects of major volcanic eruptions can temporarily mask the general warming trend resulting from an excess of carbon dioxide in the atmosphere.

key=C

2、

Some airlines allegedly reduce fares on certain routes to a level at which they lose money, in order to drive competitors off those routes.However, this method of eliminating competition cannot be profitable in the long run.Once an airline successfully implements this method, any attempt to recoup the earlier losses by charging high fares on that route for an extended period would only provide competitors with a better opportunity to undercut the airline's fares.

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

(B) Airline executives generally believe that a company that once underpriced its fares to drive away competitors is very likely to do so again if new competitors emerge.

(D)！ On deciding to stop serving particular routes, most airlines shift resources to other routes rather than reduce the size of their operations.

key=B

3、

At present the Hollywood Restaurant has only standard-height tables.However, many customers come to watch the celebrities who frequent the Hollywood

, and they would prefer tall tables with stools because such seating would afford a better view of the celebrities.Moreover, diners seated on stools typically do not stay as long as diners seated at standard-height tables.Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.

The argument is vulnerable to criticism on the grounds that it gives reason to believe that it is likely that

(C) a customer of the Hollywood who would choose to sit at a tall table would be an exception to the generalization about lingering

(D) ！a restaurant's customers who spend less time at their meals typically order less expensive meals than those who remain at their meals longer

key=C

前面有叹号的就是我选的……大家帮忙解答一下吧