A．European countries tend to support having naps.
B．Working men should have a nap regularly.
C．Adults are more likely to develop heart disease.
D．Naps may lower the chance of dying of heart disease.
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.