根据短文内容填空。
Coffee has been a part of people's lives for thousands of years, and today it is still one of the most
popular d______ (1) in the world. Many people in the world b______ (2) their busy day by
drinking a cup of coffee. They think that a cup of coffee in the morning helps them begin their day in the
r______ (3)way. So they say a cup of coffee is n______ (4) for them in the morning.
Do you know what is in the coffee that makes our bodies and brains active? It is caffeine. Caffeine
may i______ (5) a person's mental and physical abilities. For example, two cups of coffee will make
you b______ (6) faster and augment (增大) body heat. All this makes your heart b______ (7) faster,
and doctors warn that this may be a little d______ (8) .
Caffeine is f______ (9) in tea, coffee, chocolate and some other foods. A little caffeine is probably
not h______ (10) . But too much caffeine can make people nervous and sleepless.