We were told not to touch the equipment in the laboratory unless ________.
#101834
A
allowed to do
B
allowing to do
C
allowed to
D
allowing to
推荐题目
The driver could have survived but he          the seat belt.
#102832
A
had been wearing
B
hadn't worn
C
wasn’t wearing
D
didn't wear
In the past decades, sea ice _____in the Arctic as a result of global warming.
#102142
A
had melted
B
has been melting
C
melted
D
is melting
 —Have you read the book called Waiting for Anya?—Who _________ it? 
#104597
A
writes
B
has written
C
wrote
D
had written