Could you tell me ______ it takes to go from here to Beijing by air? —About 50 minutes.[ ]

The book was written in 1946, ____the education system has witnessed great changes .

I have lots of work to do now. I don’t have time ________________ you.

If you still have a problem,you can ask the police ______help.[ ]

I think zoos provide clean and safe places endangered animals to live in.[ ]