All of the following can be considered some of the obstacles artificial intelligence can hardly get over EXCEPT ______.

A．The specialists' complaints can by no means be justified and should thus be dismissed.
B．A machine itself cannot be made to think in that it usually follows the procedures set in advance.
C．Humans generally use their wisdom to assess risks, evaluate the outcomes and make a sensible decision.
D．Machines are after all machines and they will never defeat human chess players.

A．older parents should exercise more to keep up with their athletic children
B．many people are young in spirit despite their advanced age
C．older parents tend to be concerned about their aging bodies
D．taking afternoon naps is a good way to maintain energy