What can we infer from the tragic example given in the first paragraph?
A.
People rescued the man before he was drowned in the polluted water.
B.
Some people were near the man who was drowning but they did not try to rescue him.
C.
The man could have been saved if the Thames had not been so seriously polluted.
D.
The rescuers could not see the drowned man because he was carried away by the fast flowing river water.