My English-Chinese dictionary has disappeared. Who do you think ________ have taken it?[ ]

The pilot asked all the passengers on board to remain____as the plane was making a landing [ ]

It is reported that two schools，________ are being built in my hometown，will open next year.

The policeman caught the thief by ________ arm

______ the traveler of carrying drugs, the customs official stopped him and went through his suitcase.