In Papousek's experiment babies make learned movements of the head in order to ______.

A．the lights were directly related to some basic "drives"
B．the sight of the lights was interesting
C．they need not turn back to watch the lights
D．they succeeded in "switching on" the lights

A．would make learned response when it saw the milk
B．would carry out learned movements when it had enough to drink
C．would continue the simple movements without being given milk
D．would turn its head to right or left when it had enough to drink