Black clouds had completely the sun.A. blocked offB. broken outC. blocked outD. broken of

问题补充：

Black clouds had completely the sun.

A. blocked off

B. broken out

C. blocked out

D. broken off

答案：

A. blocked off

B. broken out

(答案→)C. blocked out

D. broken off

解析：考查词组：A. blocked off封堵B. broken out爆发C. blocked out遮住，挡住D. broken off折断，句意：乌云完全遮住了太阳。选C。