问题补充：
---How does Jack usually go to school?
---Heride a bike, but now hethere 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
答案：
A. used to, is used to walk
B. was used to, is used to walking
C. was used to, is used to walk
(答案→)D. used to, is used to walking
解析：
试题分析: 句意：杰克通常怎么上学？他过去骑自行车，但现在他习惯步行为了减肥。used to do过去常常做某事，be used to doing习惯做某事，固定短语，故选D
