蓄电池组应()一次进行清扫、外观检查;每季度采用断开充电机交流输入的方法进行一次蓄电池单只电压检测。
A.每半年
B.每月
C.每半个月
D.每周
参考答案:B
找出错误,将字母标号填在括号中,再将正确的写在横线上。
( ) 1. How many book are there in the bag? _______________
A B C D
( ) 2. I saw a dog in a Mondy morning. _______________
( ) 3. A fish can swim and a bird can flying. _______________
( ) 4. These ducks are in the table, too. _______________
( ) 5. What are they do? They are playing cards. _______________
至今还()研制出可以有效预防艾滋病的疫苗。
A、已有
B、没有
C、可能有