4．The babies would “smile
and speak ”at the lights because ____.
A．they succeeded in“
turning on” the lights
B．the sight of lights was
interesting
C．they need not turn back
to watch the lights
D．the lights were directly
connected to some basic “drives”
B
Human beings act in a different way from that of animals just
because they can think while animals cannot．Even
the cleverest animals cannot do things which to us seem very simple and which
small children，as soon as they learn to
talk，would be able to do．
A German scientist，who
made experiments for many years with big apes，found that his apes could use sticks as tools to pull down
bananas which they could not reach．But
they only used the stick to get a banana when both the stick and the banana
were in view at the same time．If the banana was in
front of them and the stick was behind them，they
could not use the stick．They could not bear(记住)the banana in mind long enough to look around and pickup the
stick and then use it．
The reason for this is clear．We have words for banana and stick which help us to think
about these things when they are not in sight．Even a small child knowing the words“banana”and“stick” has an
idea of their relationship and is able to think of“stick”together
with“banana”and to remember this long enough to pick up the stick from behind
and use it on the banana．
Unable to speak，animals
cannot keep their knowledge for long．That
is why they often interrupt one line of action to do something else and later
forget it completely．Human beings，on the other hand，use
language and are able to go after one thing continuously and do it with a
definite(明确的)aim．