When the teacher came into the classroom, all of us __________ the classroom.
A. are cleaning
B. were cleaning
C. cleaned
D are cleaned
---______ can we warn people not to swim here?
---By putting up signs.
A. How B. Why C. Where
---I saw the 3D printer print some cartoon characters at the science fair.
---Sounds fun! I believe such technology will be ______ used in many ways
A.widely B. difficultly C. clearly
Remember not to ask ______ questions, like the age, when you talk with an American.
A. historical B. lifelong C. private
To the heavy traffic，1 have to leave so early．
A．increase B．avoid C．spread
Wechat hongbaoisa fun way to express wishes instead of the traditional
A．partner B．product C．present