That was because the school bus was by a thick fog.
A. broke off
B. held up
C. kept up
D. turned off
网友回答
A. broke off
(答案→)B. held up
C. kept up
D. turned off
解析：句意：那都是因为由于大雾校车被延误了。A. break off打断，终止C. keep up保持D. turn off 关掉电源等B. hold up 延误,阻挡，根据句意和动词短语的意思判断B最佳。
考点:考查动词短语的用法。