I don't think she is the most beautiful _______ (type) of the five.
A sewage plant is a please where the polluted water is _______ (clean) up.
Electroinic brains are the machines that help in people's _______ (calulate)
The mistakes in the articles must be _______ (correct) one by one before they are published.
_______ (pollute) is a serious question we should pay cattention to.