急性心肌梗死主要是由于（）。

A.心肌炎

B.冠状动脉痉挛

C.冠状动脉堵塞

D.肺动脉供血不足

E.主动脉供血不足

One of the provinces in the north has          to form a new state.

A．broken down

B．broken up

C．broken out

D．broken away