【词组解析】
1. careful of/about/with 小心,注意
（1）Children must be taught to be careful of traffic.
必须教育孩子要当心车辆。
（2）Be careful about what you say.
要当心你说的话。
2. certain of /about 确信,肯定
（1）The witnesses were each perfectly certain of what they said.
证人们个个对自己所说的话十分肯定。
（2）Scientists are fairly certain about the effects of hot spots beneath the ocean floor.
科学家们确信在海底下方的热点作用。
3. chair a meeting 主持会议
（1）The next day I chair a meeting with Alibaba senior executives on countering fraud.
次日，我和几位高管共同主持了有关打击欺诈的会议。
（2）President Obama will chair a meeting on July 9 of the 17-nation Major Economies Forum on managing climate change.
奥巴马将在7月9日主持17国主要经济体论坛，讨论应对气候变化问题。
4. charge sb. with sth. 控告
（1）They that and because I was under 16, they could not charge me with anything. Besides.
没有,而他们居然相信了,并且因为我未满16岁, 他们也不能以任何罪名指控我 —— 即使。
（2）If you lay hands on me, I will charge you with assault.
如果你对我动手, 我就指控你犯人身伤害罪。
5. clear of 没有，不接触，无阻碍；无辜的；摆脱
（1）They dragged the fallen tree clear of the road.
他们把倒下的树从路上拖走。
（2）I tried to edge away until I was clear of the crowd.
我侧着身子移动,最后走出了人群。