预防麻疹的关键措施是
A.对病人要隔离至出疹后5日
B.避免易感者接触麻疹病人
C.病室每日要通风30分钟
D.普遍接种麻疹减毒活疫苗
E.流行期易感儿肌注入血丙种球蛋白
参考答案:D
根据句意及首字母提示完成句子。
1. I want to take my daughter to go to a m ______.
2. There are all k______of flowers in the store.
3. I can't f______my watch in the room.
4. You can ask (请求) s ______to help you.
5. My brother is 13 years old. He is still a s______.
甲、乙的速度比是4:3,乙、丙的速度比是2:3,那么甲、丙的速度比是( ) 。