They have been skating __________.
#40389
A
for three hours
B
since three hours ago
C
three hours ago
D
since three hours
推荐题目
The Reads __________ lunch when I got to their house. 
#36346
A
was having
B
were having
C
are having
D
is having
 My sister has learnt English _________.
#36360
A
for twelve years ago
B
since she was four
C
twelve years ago
D
at the age of four