吸烟的害处（英文文章）

Caffeine may increase a person’s mental and physical abilities （精力和体能）. For example, two cups of coffee will make you breathe faster and augment body heat （热量）. All this makes your heart beat faster, and doctors warn that this may be a little dangerous.
Caffeine is found in tea, coffee, chocolate and some other foods. A little caffeine is probably not harmful, but too much caffeine can make people nervous and sleepless.