is known to the world the Chinese in many places the old traditions.A. That; keep on B.

问题补充：

is known to the world, the Chinese in many places the old traditions.

A. That; keep on

B. which; keep out

C. It ; keep back

D. As; keep up

答案：

A. That; keep on

B. which; keep out

C. It ; keep back

(答案→)D. As; keep up

解析：考察定语从句和固定词组。As指代后面一句话的内容，在句中作主语。Keep up保持。结合句意可知D正确。句意：众所周知，很多地方的中国人都保持着很多古老的风俗。