Only when ______ the data again ______ that there was a mistake. [ ]

Do you know the reason _________ pilots turn off the plane’s lights before taking off? —The practice is for the passengers to adjust to the dark _________ an emergency.

We became good friends quickly, ______our life experiences couldn’t have been more different

eedn’t take an umbrella. It isn’t goingto rain.— Well, I don’t know. It do.

Let’s go for a walk，shall we?-It’s too late now；________，it’s beginning to rain.[ ]