Fighting an artificial greenhouse effect seems to be the greatest of environmental challenges, ________？
#64479
A
isn't it
B
does it
C
doesn't it
D
is it
推荐题目
— ______ will your father come back from New York?— In two days.
#60067
A
How long
B
How many
C
How often
D
How soon
The mother didn’t know _____to blame for the broken glass as it happened while she was out.
#64777
A
who
B
which
C
they
D
that