(AFA - 2010)All light on the nightOur cities and t

(AFA - 2010)

All light on the night

Our cities and towns are far from silent at night. As most of ______ are going to bed, a lot of workers are just going to their jobs. It is estimated that up to a fifth of the working population carries out its duties at night - running hospitals and
maintaining power stations, for example.

There is one problem: They have the same biological clock as day workers. Night workers often have trouble sleeping through the day, and sometimes find ______ harder to stay awake, which means mistakes are more likely to happen. Dr Lawrence Smith, a psychologist, [13] discovered that among people who¹ do the same job, night workers suffered 20% more injuries than day workers.

He is now testing the theory that the light can be used to fool the human body clock.The body clock appears to be influenced by light, because one chemical at its disposal is sensitive to light.

Adapted from Advance your English

We can replace the pronoun 'who' (ref. 1) by