How much shall I pay for the phone call? —-You ____ .This is free of charge.

What happened to you just now, Daisy?— My key was missing. I had to ______ the door open.[ ]

Her teacher helped her so much that she bought him a beautiful pen _________.

Listen! Is it Linda singing in the next room –No, it __________ be her. She is still in Shanghai.

why not swim in the river—oh, no. our teacher told us _____ here. It’s dangerous.