面颊部有短暂的反复发作的剧痛,检査时除“触发点”外无阳性体征,常见于

A．特发性面神经麻痹

B．三叉神经痛

C．症状性癫痫

D．面肌抽搐

E．典型偏头痛

There has been a nation-wide shortage of building materials, （） which the trade is only just recovering.

A. for

B. on

C. at

D. from