Many air flights _________because of the eruption of the volcano, in _______case, many passengers had no choice but to take a train. 
#103338
A
had been cancelled; which
B
have been cancelled; what
C
had been canceling; that
D
have been canceling; where
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 Selecting a mobile phone for personal use is no easy task because technology __________ so rapidly.
#104438
A
is changing
B
has changed
C
will have changed
D
will change
In the past several weeks, many cities in Northern China        from heavy fogs and  severe cold.
#99857
A
had suffered
B
have been suffering
C
were suffered
D
suffered
---Why do you keep looking back? ---I have a feeling that we _______.
#103489
A
were followed
B
have been followed
C
are being followed
D
are following