Space exploration began in the 1960s, and since then about five hundred people into space.
#101989
A
have traveled
B
traveled
C
had traveled
D
are traveling
推荐题目
—The door is still open.—How come? I mean, I _________ to lock it then.
#100493
A
remembered
B
would remember
C
remember
D
had remembered
I can’t leave. She told me that I_____ stay here until she comes back.
#104199
A
can
B
must
C
will
D
may
The computer looks old, but it _________ just half a year ago.
#103884
A
has been bought
B
was bought
C
is bought
D
will be bought
By the time he _____ back last night, we had got 200 pictures of the Chang'e-3 lunar probe.
#99993
A
came
B
had come
C
was coming
D
would come
We’ve been told the good news, but when and where to go for the exciting paid vacation _______ yet.
#101524
A
are not discussed
B
have not been discussed
C
is not being discussed
D
has not been discussed