The old man was telling a funny story, surrounded by many kids, _________ with fascination.

A．all of whom listened

B．all of whom listening

C．all of them listened

D．all of them were listening

涨圈与勾贝槽之间的间隙（）毫米之间，使涨圈即可以在槽内上下活动发挥其弹力，又能保持汽密。