问题补充：
Old Henry take his dog for a walk after supper. But these days he is too weak to do that.
A. has to
B. is able to
C. used to
D. got used to
答案：
A. has to
B. is able to
(答案→)C. used to
D. got used to
解析：have to 不得不 be able to能够做某事get used to sth习惯于某事 ，句意：亨利老人过去常常晚饭后去遛狗。但现在他太虚弱了而不能这么做了。故选C.
