根据汉语提示完成句子。 1. Please _____ (举手) when you'd like to answer my questions. 2. Some parents _____ (担心把手机给……) to their children. 3. _____ (你认为) they will come before 10 o'clock? 4. My brother won first place in the _____ (400米比赛). 5. Don't _____ (同陌生人交谈) with your cell phone.