—Every day, my mother tries to spare some time to chat with me,        she  is very tired after a whole day’s hard work.

—You are lucky to have such a great mum!

A．unless

B．whether

C．although

D．until

合模时，导柱与导套间呈（）。

A、过孔

B、间隙配合

C、过渡配合

D、过盈配合