--When _____ the abacus _____?   -- In the sixth century by the Chinese people.
#44867
A
is, invented
B
did, invent
C
was, invented
D
does, invent
推荐题目
A new house ___ at the corner of the road.
#44460
A
is building
B
is being built
C
been built
D
be building
 This movie ________ on the Internet.
#44410
A
watch
B
watches
C
can watch
D
can be watched
The dictionary mustn’t ________ from the library.
#44684
A
take away
B
taken away
C
are taken away
D
be taken away
Stamps are usually used _____letters.
#44752
A
to sending
B
to send
C
for send
D
for sent