问题

Pollution is a serious ___________ in China . PM2.5 has been increasing in recent years.
A:wrong
B:question
C:problem
D:matter;
B:question
C:problem
D:matter;
正确答案是:
同类题型
The letters for the boss ________ on his desk but he didn’t read them until three days later.[ ]
Will you please show me the way to the only tallbuilding ___stands near the post office?
erthere—there’saverylong,windingpath_________uptothehouse.
It suddenly _____ to me that we could ask our neighbors to help us.