题目

如图所示，加热烧瓶中的水使之沸腾。水蒸气从铜管喷出，把火柴靠近管口P处，火柴被加热，迅速移开火柴，火柴开始燃烧。下列说法错误的是（    ） A、水沸腾，水分子质量和体积增大 B、P处水蒸气的作用是使火柴温度达到着火点 C、火柴移离水蒸气，与氧气充分接触，从而燃烧 D、火柴燃烧的产物含有二氧化碳和水 阅读下面短文，根据文后各题的具体要求回答问题。 　　The curtain on the 2008 US presidential election finally rose last month as John McCain and Barack Obama were formally nominated(提名)as candidates of the two major parties．This may be one of the hardest decisions voters have to make between two appealing candidates． 　　The big question for voters, as they face both an economic downturn and international threats, is：who will they elect?A young first-term senator promising change and new ideas, or a longtime senator with strong military experience and a reputation as a maverick(特立独行的人)? 　　American voters have never seen a candidate quite like Obama．He has a white mother from the US and a black father from Kenya who left the family when Obama was very young．He spent part of his youth in Indonesia． 　　His supporters say Obama’s childhood gives him the advantage to repair the recent damage done to America’s image abroad．His opponents focus on his inexperience, noting he hasn’t finished his first term in the Senate． 　　However, McCain has a very different life story．He grew up in a Navy family and was a pilot during the Vietnam War in the 1960s．When Obama was in kindergarten in Indonesia, McCain’s plane was shot down over Vietnam and he became a prisoner of war, where he was held for five years unless he disowned America, but he refused． 　　So in the end, the election may hinge on(以…为转移)several factors that are hard to judge：Will Obama’s race matter to a significant number of voters?Will working-class whites who tended to support his primary opponent, Hillary Clinton, vote for Obama?And perhaps most important of all, will swing(摇摆)voters be more drawn to Obama’s vision(远景规划)or to McCain’s experience? 　　Whatever happens, one thing is clear：Whoever walks into the White House on January 20, 2009, will find enormous challenges waiting for him in the Oval Office(美国总统办公室), both at home and abroad． 1．Why was McCain taken in prison in Vietnam?(回答词数不超过8个) 2．What made the result of the election hardest to predict according to the author?(回答词数不超9个) 3．What do the underlined words”enormous challenges”refer to according to the passage?(回答词数不超过7个)