The robot needs _______ once a month. And we will check it for you for free.
#48844
A
to check
B
checked
C
checking
D
to checking
推荐题目
---I often chat with my friends on the Internet.---You are so smart! Will you please tell me ________?
#49449
A
how to do
B
how to do it
C
how to use
D
when can I use it