When a new disease breaks out, experts must ________ what to do in the fastest way.

Can you tell me how to learn English well? — Do more speaking, I think, ______ you will not be good at spoken English[ ]

Could you tell me ______— Sure. We will meet at the school gate.

Now there’s a system _________ the waste is disposed of using the principles of ecology.

There is ____ “u” and _____ “r” in the word “number”.