--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
The game __________ by all the students.
#44707
A
enjoys
B
enjoyed
C
enjoying
D
is enjoyed
A new cinema _ in our city last year.
#44932
A
built
B
was built
C
will build
D
is built
Nobody ______ to go into the laboratory without permission (允许).
#44894
A
allows
B
is allowed
C
promises
D
is promised