Time and how we experience it have always puzzled us. Physicists have created fascinating theories, but their time is measured by a pendulum（钟摆）and is not psychological time, which leaps with little regard to the clock or calendar. As someone who understood the difference remarked, “When you sit with a nice girl for two hours it seems like a minute, but when you sit on a hot stove, a minute seems like two hours.”
Psychologists have long noticed that larger units of time, such as months and years, fly on swifter wings as we age. They also note that the more time is structured with schedules and appointments, the more rapidly it seems to pass．For example, a day at the office flies compared with a day at the beach. Since most of us spend fewer days at the beach and more at the office as we age, an increase in structured tune could well be to blame for why time seems to speed up as we grow older．
Expectation and familiarity also make time seem to flow more rapidly. Almost all of us have had the experience of driving somewhere we’ve never been before. Surrounded by unfamiliar scenery, with no real idea of when we’ll arrive, we experience the trip as lasting a long time. But the return trip, although exactly as long, seems to take far less time. The unfamiliarity of the journey has become routine. Thus taking a different route on occasion can often help slow the clock.
When days become as identical as beads（小珠子）on a string, they mix together, and even months become a single day. To fight this, try to find ways to interrupt the structure of your day—to stop time. Learning something new is one of the ways to slow the passage of time. One of the reasons the days of our youth seems so full and long is that these are the days of learning and discovery. For many of us, learning ends when we leave school, but this doesn’t have to be.
The quotation（引用语） in the first paragraph is used to indicate ______.

A．physical time is different from psychological time

B．time should not be measured by a pendulum

C．psychological time is quite puzzling

D．physical theory has nothing to do with the true sense of time

Why do units of time fly faster as we grow older?

A．Our sense of time changes.

B．We spend less time at the beach.

C．More time is structured and scheduled.

D．Time is structured with too many appointments.

What is the main idea of the passage?

A．It gives various explanations about time.

B．It explains why time flies fast and how to slow it down psychologically.

C．It shows the different ideas of physicists and psychologists on time.

D．It describes how we experience time psychologically.