The abacus was invented ________ by Chinese people.

1. A.
   in the sixth Century
2. B.
   in the sixtieth Century
3. C.
   in the sixteenth Century
4. D.
   in the six Century

The abacus (算盘) ______ used in China centuries ago.

[    ]

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