Some teenagers hold the view that parents ____ a full understanding of their children.

A．lack in

B．lacking of

C．lack of

D．lack

《学记》中"藏息相辅"教学原则强调（）。

A.教学要遵循一定顺序进行

B.启发式教学

C.教学要把握最佳时机

D.课内与课外相结合