检查口、清扫口和室内检查井等清通设备，其作用是( )。
A．疏通排水管道
B．排除系统内臭气
C．保障排水畅通
D．减少管内压力
参考答案：A,C
不得从事疫苗经营活动的（）
A．疫苗生产企业
B．药品零售企业
C．省级疾病预防控制机构
D．设区的市级疾病预防控制机构
E．国家疾病预防控制机构
用括号内单词的适当形式填空.
1. My sister always _____ (do) some _____ (read) in the evening.
2. Last year I _____ (go) to Shanghai.
3. Yesterday he _____ (do) his homework at home.
4. Last night we _____ (go) to the movies.
5. I _____ (have) a busy day last weekend.
6. My brother _____ (stay) at home last night.
7. They _____ (enjoy) themselves in the party last Sunday.
8. Did you _____ (go) to the movies last night?
9. Li Lei practices _____ (speak) English every day.
10. I _____ (clean) my room two days ago.
