【正确答案】 B

【答案解析】[解析] 1-10
We define time travel to mean departure from a certain place and time followed (from the traveler's point of view) by arrival at the same place at an earlier time (from the sedentary observer's point of view). Time travel paradoxes arise from the fact that departure occurs after arrival according to one observer and before arrival according to another. In the terminology of special relativity time travel implies that the time-like ordering of events is not invariant. This violates our intuitive notions of cause-effect relation. However, intuition is not an infallible guide, so we must be careful. Is time travel really impossible, or is it merely another phenomenon where "impossible" means "nature is more mysterious than we think"? The answer is more interesting than you might think.
The B-movie image of the brave chrononaut climbing into his time machine and watching the clock outside spin backwards while those outside the time machine watch the "him" revert to babyhood is, according to current theory, impossible. In current theory, the arrow of time flows in only one direction at any particular place. If this were not true, then one could not impose a 4-dimensional co-ordinate system on space-time, and many nasty consequences would result. Nevertheless, there is a setting that is not ruled out by present knowledge. This usually requires an unusual space-time topology (due to wormholes or strings in general relativity) which has not yet seen, but which may be possible. In this setting the universe is well-behaved in every local region; only by exploring the global properties can one discover time travel.
It is sometimes argued that time travel violates conservation laws. For example, sending mass back in time increases the amount of energy that exists at that time. Doesn't this violate conservation of energy? This argument uses the concept of a global conservation law, whereas relativistically invariant formulations of the equations of physics only imply local conservation. A local conservation law tells us that the amount of stuff inside a small volume changes only when stuff flows in or out through the surface. A global conservation law is derived from this by integrating over all space and assuming that there is no flow in or out at infinity. If this integral cannot be performed, the global conservation does not follow. So, sending mass back in time might be all right, but it implies that something strange is happening. Why shouldn't we be able to do the integral?
The possibility of time travel in General Relativity has been known at least since 1949. The General Relativity space-time found by Godel has what are now called "closed time-like curves"(CTCs). A CTC is a world line that a particle or a person can follow which ends at the same space-time point (the same position and time) as it started. A solution to General Relativity, which contains CTCs, cannot have a space-like embedding — space must have "holes" (as in donut holes, not holes punched in a sheet of paper). A would-be time traveler must go around or through the holes in a clever way.

题目信息对应于独白第一句话：We define time travel to mean departure from a certain place... by arrival at the same place at an earlier time...，即时间旅行指的是从某个地方出发，而到达同一个地方的时间要比出发的时间早。但题目与此句之间的不同显而易见。

【正确答案】 A

【答案解析】本题对应于独白第二句话：Time travel paradoxes arise from...according to another，即时间旅行这一悖论源于这样一种事实：对于一个观测者来说出发后于到达，而对于另一个观测者来说则先于到达。题句只是将这一句中的paradoxes换成了theory，而将arise from换成了developed from而已。

【正确答案】 A

【答案解析】本题对应于独白第四句话：This violates our intuitive notions of cause-effect relation(这违背了我们关于因果关系的直觉观念)，其中的主语this是承接前一句指special relativity time travel(特殊的相对时间旅行)，而violates就是题句中的goes against。本题根据常识也可确定它是正确的。

【正确答案】 B

【答案解析】本题对应于独白第一段第五句。该句指出：However，intuition is not an infallible guide(然而，直觉并非是万能的引导者)，但作者并未断然指出我们是受了误导才觉得时间旅行违背了我们的直觉，题句实际上是误解了此句中infallible一词的意思。

【正确答案】 B

【答案解析】独白第二段提到了B-movie(B级电影，即投资少的劣质电影)。该段第一句指出，B-movie中勇敢的时间宇航员爬进时间机器，看着外面的时钟倒转，而时间机器外面的人则看着这个“他”变成婴儿，这种情况按照现在的理论来说是不可能发生的。然后作者分析了不可能的原因，并且指出根据奇异时空拓扑学这是有可能的。所以，作者并没有说我们关于因果关系的直觉观念是错误的，也没有说B-movie是证明这一观念错误的有力证据，故题句是错误的。

【正确答案】 A

【答案解析】本题对应于独白第二段最后一句。在该句中，作者用倒装句强调说：only by exploring the global properties can one discover time travel(只有通过研究整个世界的性质才能发现时间旅行)，题句只是将其中的only...can...改换成了have to，故是正确的。注意，此处的globe/global指的是“世界/世界的”。

【正确答案】 B

【答案解析】独白第三段提到了invariant formulations of the equations of physics，指出它们only imply local conservation(只意味着局部守恒)，然后指出，全面守恒定律源于局部守恒定律，而全面守恒定律则是那些认为时间旅行违反了能量守恒定律的人所用的概念。由此可知，invariant formulations of the equations of physics应当是使得时间旅行不可能存在，题句的意思正好与此相反，故是错误的。

【正确答案】 A

【答案解析】本题对应于独白第三段第六句：A global conservation law...assuming that there is no flow in or Out at infinity(全面守恒定律……认为在无限远处没有物质流入或者流出)，题句与此意思一致，只是表达方式不一样，故是正确的。

【正确答案】 A

【答案解析】本题需要在听清材料的基础上进行一定的推断。独白最后一段第一句指出：The possibility of time travel in General Relativity has been known at least since 1949(广义相对论关于时间旅行的可能性至少早在1949年就为人们所知了)，根据时间计算，该理论应当是在半个多世纪前提出的，这与题句的意思正好一致，故本题正确。

【正确答案】 B

【答案解析】在独白的最后一句中，作者指出：A would-be time traveler must go around or through the holes in a clever way(一个可能的时间旅行者必须用一种巧妙的方式绕过或者穿过这些洞)，由其中的would-be以及整个句意不难看出，作者并没有否定时间旅行的可能性，因此题句是错误的。