We have known for a long time that flowers of different plants open and close at different time of day. Yet no one really understands why flowers open and close like this at particular times. It is not as simple as we might think, as new experiments have shown. In one experiment, flowers were kept in darkness. We might expect that the flowers, without any information about the time of the day, did not open as they usually do. In fact, they continued to open at their usual time. This shows that they have some mysterious (神秘的) way of knowing the time.
Their sense of time does not depend on information from the outside world; it is, so to speak, inside them, a kind of “inner clock”. This discovery may not seem to be very important. However, it was later found that not just plants but also animals including man have this “inner clock”which controls working of their bodies and their activities.
Human beings, then, are also controlled by this mysterious power. Whether we wish it or not, it affects such things in our life as our need for sleep, our need for food. And our ability to concentrate(集中).
One experiment was done for finding out        .

A．when different flowers open and close

B．if flowers have a mysterious way of knowing the time

C．how flowers are used to tell the time in the darkness

D．why flowers open and close at particular time

Before the experiment arrived at a conclusion, people had thought that the flowers     .

A．would never open in darkness

B．would change their usual time to open

C．would continue to open at their usual time

D．would open earlier than the usual time

That flowers have the sense of time is related to      .

A．sunlight

B．weak light

C．the “inner clock”

D．the information from the outside world

From the passage, we know that      don’t have mysterious power inside.

A．wild animals	B．human beings
C．all creatures(生物)	D．lifeless things

We may know that if we make good use of the ‘inner clock’,       .

A．we will have more strength to do our work.

B．clocks or watches are no longer useful to us

C．we will be able to live as long as we wish to

D．human beings will need less sleep, less food or less movement