--When _____ the abacus _____?   -- In the sixth century by the Chinese people.

--When _____ the abacus _____?   -- In the sixth century by the Chinese people.

Yao Ming is a popular basketball player ____ the Chinese

people.

--When _____ the abacus _____?  

-- In the sixth century by the Chinese people.

1. A.
   is, invented
2. B.
   did, invent
3. C.
   was, invented
4. D.
   does, invent