_______ the calculation is right, scientists can never be sure that they have included all variables and modeled them accurately.
My new pen ______. Who ______ have taken it?
— Can I smoke here? — Sorry. We don’t allow ______ here.
— Where is my dictionary? — You ______ it in the wrong place.
She spends her money______ books ______ on clothes.
— David hasn’t come yet. —I think he will ______ soon, for he means what he says.