问题
Pollution is a serious problem. Scientists have _____ some good ways to save it.
A:come up with
B:come on
C:come out
D:come up
B:come on
C:come out
D:come up
正确答案是：
同类题型
I often go to school _________ 7:30 _________ the morning. [ ]
Peter，is there anything else you want to know about China?—Yes，I am still wondering __________ .
Can I have ________cakes, please?— Sorry, I don’t have ________cakes in my fridge.
The doctor tells me I should eat ______ meat and take ______ exercise.