-Do you mind my taking this seat?

-____   . It's for Mr. Smith.[ ]

A. Not at all          

B. Yes, pleaseI

C. Yes. of course not    

D. You'd better not

侧开门门锁开闭作用良好，作用不良时更换或调修；零部件丢失补装，锁杆弯曲调修；焊缝开裂时焊修；上门锁杆插入量小于（）时更换或调修。上门锁杆与手把间的螺母与螺杆须点焊固定。

A.10mm

B.20mm

C.30mm

D.40mm