问题补充：
Long ago, man used to with his hands but now man is used to with machines, and sometimes a robot is used to instead of people.
A. work, working, work
B. work, working, working
C. working, work, working
D. working, work, work
答案：
(答案→)A. work, working, work
B. work, working, working
C. working, work, working
D. working, work, work
解析：原文意思，很久以前，人类常常用双手劳动，但是现在人们习惯了使用机器，有时候机器人被用来工作，代替了人。used to do sth. 过去常常干某事（现在已不再这样），be used to (doing) sth. 习惯于干某事（to为介词），be used to do sth.被用来干某事，故选A。
