题目内容：

    When one tried to unify gravity with quantum mechanics(量子力学), one had to introduce the idea of ‘imaginary’ time. If one can go forward in imaginary time, one ought to be able to turn round and go backward. This means that there can be no important difference between the forward and backward directions of imaginary time. Yet there is a big difference between the forward and backward directions of ‘real time’ in ordinary life. Imagine a cup of water falling off a table and breaking into pieces on the floor. If you take a film of this, you can easily tell whether it is being run forward or backward. You can tell that the film is being run backward because this kind of behavior is never observed in ordinary life.

The explanation that is usually given as to why we don’t see broken cups gathering themselves together off the floor and jumping back onto the table is that it is forbidden by the second law of thermodynamics(热力学). This says that in any closed system disorder, or entropy(熵), always increases with time. In other words, it is a form of Murphy’s law: things always tend to go wrong! An intact cup on the table is a state of high order, but a broken cup on the floor is a disordered state. One can go readily from the cup on the table in the past to the broken cup on the floor in the future, but not the other way round.

The increase of disorder or entropy with time is one example of what is called an arrow of time, something that tells the past from the future, giving a direction to time. There are at least three different arrows of time. First, there is the thermodynamic arrow of time, the direction of time in which disorder or entropy increases. Then, there is the psychological arrow of time. This is the direction in which we feel time passes, the direction in which we remember the past but not the future. Finally, there is the cosmological arrow of time. This is the direction of time in which the universe is expanding rather than contracting.

1.How does ‘imaginary time’ differ from ‘real time’ according to the passage?

A. Imaginary time is more important than real time in science.

B. Directions mean less to imaginary time than to real time.

C. One can go backward in real time but can’t in imaginary time.

D. It is harder to tell directions of real time than of imaginary time

2.What’s the purpose of writing about a cup of water falling off a table?

A. To define the forward and backward directions of real time.

B. To tell the backward direction from the forward direction of real time.

C. To show real time is more scientific than imaginary time in ordinary life.

D. To prove there’s a big difference between the directions of real time.

3.Why don’t we see broken cups gathering themselves together off the floor and jumping back

onto the table?

A. It doesn’t agree with the second law of thermodynamics.

B. Things will quickly go wrong for entropy increases with time.

C. There is an interchange between a state of high order and a disordered state

D. All above.

4.The underlined word in the last paragraph is closest in meaning to ______.

A. universal B. physical

C. technological D. geographical