It’s easy _________us _________ plant more trees here.
Tom and Mary _______ to China last month.
--- What’s the use of this kind of fuel(燃料) ?--- It can make the train __________ fast.
---Help yourself to some chicken , Jim . ---__________________
In our class, Andy is the __________ . He always makes everybody laugh .
---The classroom is not________ clean ______it was yesterday .---Sorry, I forgot to clean it.