This machine is very easy______. Anybody can learn to use it in a few minutes. 

Two years later, her brother disappeared in the war, never ________ again.

I’ll spend the evening ______ in your room waiting for the thief to arrive.

The professor has received the letter ____ to give a lecture in ftinceton Institute.

Children ______ on healthy diets are more intelligent compared with their junk food eating peers, new research suggests.