高等继续教育 / 专科英语II
正确率：100%
题型描述: 单选题
When ＿＿＿＿＿＿＿＿＿ this machine, you must read the instructions first.
A.having used
B.using
C.to use
D.use
When ＿＿＿＿＿＿＿＿＿ this machine, you must read the instructions first.
A.having used
B.using
C.to use
D.use
参考答案：