Americans are nervous ____________ the prospect of a nuclear-armed Iran, but also worry

__________ the ability of the United States and the United Nations to deal with the situation.

A．about; about

B．to; about

C．for; about

D．for; for

先天性心脏病引起的紫绀属于下列那种紫绀

A．中心性紫绀

B．周围性紫绀

C．肠源性紫绀

D．混合性紫绀

E．先天性紫绀