He found very difficult the math problem．
#52196
A
that；to solve
B
this；solving
C
it；to solve
D
it；solving
推荐题目
Every year, we ______ a school trip to Zhou Enlai Memorial Hall.
#59101
A
come on
B
get on
C
work on
D
go on
－How long do you think the terrible weather will _______?－Why not listen to the weather report?
#61884
A
appear
B
last
C
change
D
discover
— How long have you ________?— For three days.
#63433
A
got a headache
B
fallen ill
C
caught a cold
D
had a cough