Scientists study human brains work to make computers.
I wondered what difficulty he had _________ the plan?
My friend, David, was not used __________ by air, so he felt unwell.
The naughty boys would play ______trick on ______ neighbours who didn’t give them any sweets on Halloween.
Although he is very young, he is much more experienced than others _____ working ability.
The three-year-old girl’s behaving _____ at the table surprised all the other guests and won her a lot of kisses.