A Direct Method teacher is usually found using techniques such as______.

A．direct association and conversation practice

B．question and answer exercises

C．error correction and dictation

D．all of the above

在鼠笼式异步电动机反接制动过程中，当电动机转速降至很低时，应立即切断电源，防止（）。

A.损坏电机

B.电动机反转

C.电动机堵转

D.电机失控