Swimming is, of course, interesting. But ______ we plan to go swimming, being safe must come first.
句意：游泳当然很有趣。但是当我们计划去游泳时，安全必须放在第一位。
考查连词辨析。though尽管；when当……时；unless除非。根据题意“____我们计划去游泳，安全必须放在第一位”，结合选项可知此处用when符合题意，在句中引导时间状语从句。故选B。
Swimming is, of course, interesting. But ______ we plan to go swimming, being safe must come first.
The clever boy called 120 _______ his mother fell down in the kitchen.
—I'm afraid we can't work out the math problem________the teacher helps us.
—That's true. It's too difficult.
I don’t like Sun Cinema ________ it has bad service.
Check what you have written _______ you hand in your application form.
We still know little about the Moon _____ men have landed on it.
The movie Nezha is_______ educational ____ I want to see it again.
You can surf the Internet ______ you want to know more about the 2020 World Middle School Games.
—How time flies! The middle school life is coming to an end.
—Yes. We have to say goodbye, ________ our friendship will last forever.
Mike and Jim's room is tidy, ______ their sister's not.
