After Jack had sent some e-mails, he _______ working on his project.
#102159
A
had started
B
has started
C
started
D
starts
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The boys followed the marks that they ________, until finally they found their way back to the campsite.
#100125
A
left
B
have left
C
had left
D
have been left
Every possible means ________, but the teacher as well as the students ________ found a solution to the problem yet.
#102485
A
has been tried; hasn’t
B
has tried; haven’t
C
have tried; haven’t
D
have been tried; hasn’t
Every possible means to prevent the air pollution, but the sky is not still clear.
#101886
A
is used
B
are used
C
has been used
D
have been used
---Peter, where did you guys go for the summer vacation?---We _______ busy with our work for months, so we went to the beach.
#99359
A
were
B
had been
C
have been
D
will be