It never _____  humans until the mid­1990s that some animals can be cloned.
#92718
A
occur
B
is occurred
C
occurred to
D
occurred
推荐题目
Though we are not walking slowly, I still think that it won’t be _________ he _________up with us.
#92357
A
long before; catches
B
before long; catches
C
for long; caught
D
long until; will catch
______ unless I call you. 
#94749
A
Please come
B
Not come in
C
Don’t come in
D
Come in
It is reported that women with demanding jobs are almost __________ to suffer a heart attack .
#93356
A
as likely twice
B
likely twice as
C
twice likely as
D
twice as likely