Present simple

From birth, we.......(spend) a third of lives asleep, but scientist still........(not/know) exactly why.

Why..........(we/have) problems sleeping?

We.......(work) long hours and we rarely ......(go) to bed at sunset.

Why.....(we/sleep ) differently?

It.......(depend) on the time of years and also our age.

Teenagers usually ......(need) more sleep than adults

Lots of elderly people.......(not/sleep) longer than four or five hours at night,

but they often ......(take) naps during the day

In morden society, many adults.........(not /get) the seven or eight hours sleep they need evrey night.