As a recent survey states, people can hardly enjoy a clear blue sky because of the high level of PM 2.5.
A. in trouble
B. on purpose
C. as usual
D. in ruins
网友回答
A. in trouble
B. on purpose
(答案→)C. as usual
D. in ruins
解析：A. in trouble有困难，B. on purpose故意地，C. as usual像平常一样，D. in ruins成为废墟，句意：正如最近 的调查表明的，人们几乎不能象平常一样享受清澈的蓝天，因为PM2.5的高水平。选C。