I like __________in the early morning when the air is fresh and I can take a walk around the garden.

A．that

B．it

C．which

D．what

在内螺纹铜管拉伸过程中，油气润滑加油应（）

A.油杯内油用完后加油

B.一直充满整个油杯

C.保持油杯内油位在上.下限位之间

D.B+C