Question

Barrack Obama __________ President of the United States since 2010.

A．became a

B．has become a

C．has turned

D．has been

Answer 1

D

试题分析：Barrack Obama自从2010年一直是美国的总统。和since 2010连用，用现在完成时，而且因为是一段时间，所以不能和短暂动词become连用，所以选D。