A．Naps may help to improve work efficiency.
B．Naps may help workers work for longer hours.
C．Naps may stop workers from developing heart disease.
D．Naps during daytime are required by many workers.
A．The longer our nap is, the more energy we will get.
B．A 20-minute nap will help to restore our energy.
C．A short-time nap does less help to our body.
D．We usually don't want to wake up when taking a nap.
A．They tell people how to release stress.
B．They teach people to be mentally healthy.
C．They show people how to do better work.
D．They focus on interpersonal relationships.