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
[05] 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
[10] sometimes find ______ harder to stay awake, which
means mistakes are more likely to happen. Dr
Lawrence Smith, a psychologist, discovered that
among people who do the same job, night workers
suffered 20% more injuries than day workers.
[15] 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' (line 13) by
