TEST-1 BIOLOGICAL CLOCK
It was long ago noted that 1)_________plants open and close at different times of the day. In
fact, in the 19th century they used to make gardens in the shape of a 2) _________face with
different times. It was possible to tell the 3) ________just by looking at this 'flower clock'. No
one really understands why 4)________open and close at particular times,
but recently some
interesting experiments have been done. In one, flowers were placed in a laboratory in constant
darkness. One might predict that those flowers, not having any information
about the day, would
not 5)______, as they usually do. But in fact they continue to open as if they were in a normal 6)
__________. This suggests that they have some mysterious way of keeping time. They have, in
other words, a kind of 'biological clock'
TEST-2 ACID RAIN
Acid rain is now a familiar problem in the industrialized countries in Europe.
Gasses like sulphur
dioxide and nitrogen oxide are produced by power stations and cars. The 1)________ dissolve
in rainwater, and this makes the acid 2)______,
which damages trees, rivers and streams. Acid
rain is also capable of 3)___________ some rocks and buildings made of soft rock, such as
limestone, are particularly affected. The acid rain attacks the 4) ________ , and so carvings and
statues are eroded much more quickly. Scientists estimate the rate of
wear to be about a
millimeter of stone every twelve years. That's enough to have caused some of the ancient 5)
_________to become seriously damaged already.