I was about to walk over to Tom’sseat when he ____ and left.

单项选择（每题1分）We must think twice _____ we make the final decision

We __________ pay to get into the concert. It’s free.

It is _____ classroom that can hold 100 students. [ ]

TheideapuzzledmesomuchthatIstoppedforafewsecondstotryto________.