If you are having trouble falling asleep, you are in good company. About 65% of Americans said they have sleeping problems a few nights each week, according to a recent study by the National Sleep Foundation. Sleeping too little can lead to a higher risk of becoming fat and getting depressed(沮丧的). But before you go to a doctor for advice, it is worth examining your sleeping habits one more time. Some of your favorite evening habits may have something to do with the sleeping problems.
1. Setting a Bright Alarm Clock.
The light of your bright alarm clock can prevent you from falling asleep. You can make your room as dark as possible. Cover the bright numbers with a book or consider buying a small travel clock. Your cellphone alarm may also do the trick.
2. Counting Sheep
When you just can't fall asleep, it's useless to stay in bed to count sheep. If you've been trying to fall asleep for more than 30 minutes, the National Sleep Foundation suggests you get up to do some reading or watch TV for a while. Such activities will make you sleepy. Before you know it, you'll be going back to bed really tired.
3. Exercising Late at Night
Daytime workouts(锻炼) will keep you full of energy for hours. That's why you don't want to exercise within three hours of hitting the sack. Fierce(剧烈的)physical activity raise your body temperature and pumps your energy level-both are bad for a good night's sleep.
What can we learn from the first sentence of the passage?

A．It's not good to fail to fall asleep at night.

B．People in a good company often have sleeping problems.

C．There are many people who have sleeping problems.

D．You should find someone to talk to if you can't fall asleep.

The underlined part "hitting the sack" in the last paragraph means "______".

A．going back home

B．going to bed

C．going to the gym

D．falling asleep

Which of the following is NOT mentioned in the passage?

A．The bad results of getting too little sleep.

B．Why the bright alarm clock keeps you awake.

C．What to do if you can't fall asleep after 30 minutes.

D．Why watching TV and reading books make people sleepy.

By writing the passage, the writer mainly wants to tell us _______.

A．why so many people can't sleep well at night

B．how to enjoy a good night's sleep

C．that sleeping problems are troubling more and more people

D．that people may solve their sleeping problems by changing some habits