---How does Jack usually go to school?  

---He_____________ride a bike, but now he_______________there to lose weight.

A．used to, is used to walk

B．was used to, is used to walking

C．was used to, is used to walk

D．used to, is used to walking

柴油机不在保养周期更换机油时，（）机油滤清器。

A、应同时清洗

B、不要清洗

C、只清洗粗

D、只清洗离心式