干燥器在日常巡检时注意干燥器旋风分离器（）是否正常。

Questions 16 to 20 are based on the following talk.

A. Chronic insomnia is a rare condition compared with apnea or narcolepsy.
B. Almost everybody has chronic insomnia once in a while.
C. The cause for chronic insomnia is most often psychological.
D. There is no effective cure for this type of sleep disorder.