answer the phone when the cell phone is being charged, for it ________ be very dangerous sometimes.

The Greens ________to Beijing and ________fun there last summer.

What did you do this morning —I went ________.

下列句子中加点字的活用，与其他三句不同的一项是（ ）

In the Olympic Games all athletes should play fair ________ the rules, but some often take drugs to accomplish their aims