--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
An official _____ by some reporters on food problems in Shanghai yesterday.
#44962
A
is interviewing
B
is interviewed
C
was interviewing
D
was interviewed
You have to be 18 years before you _________ to drive a car.
#44890
A
are allowed
B
are
C
allowed
D
allow
While he            the bus, he             a book.
#44868
A
was waiting for, read
B
waited for, was reading
C
was waiting for, was reading
D
waited for, read