根据句义完成句中已给出首字母的单词。
1.Please keep your v________ down,the baby is sleeping now
2.My brother is not old enough to d________ a car.
3.P________ my teacher will come,but I'm not sure.
4.Please speak c________,or I can't understand you.
5.The doctor asked Mr. Wang to give up s________,because it’s bad for his health.
1.voice 2.drive 3.Perhaps 4.clearly 5.smoking