Scientists will have to come_______ new methods of increasing the world’s food supply.

— Did you remember to give Mary the money you owed her?— Yes, I gave it to her ________ I saw her.

It’s always difficult being in a foreign country, ________ if you don’t speak the language.

Wei Hua told me that Wu Dong was＿＿＿＿＿＿＿ill. 

It is ______ to rain this afternoon.