A dark cloud is a ________ of thunderstorm.
#6254
A
symbol
B
sign
C
mark
D
signal
推荐题目
____ in the area reported _____ three people robbing the bank with their heads wrapped in stocks.
#5590
A
Witness; to look at
B
Witnesses; seeing
C
Witnesses; looking out
D
Witness; to see
I didn’t mean to break your vase—it was just ______. 
#5437
A
an accident
B
an advantage
C
an agreement
D
an experience