晶闸管只要（）就一定关断。
A、阳极加上反向电压
B、门极加上反向电压
C、门极不加电压
D、输出负电压
参考答案：A
看图，选择合适的单词。
l. This is our________. [ ]
A. playground
B. canteen
C. garden
2. -Where's Miss White?
-She's in the _________.
A. classroom
B. library
C. teacher's office
Our ____________ is beautiful.[ ]
A. home
B. school
C. library
4. Go to the____________. [ ]
B. teacher's office
C. canteen
85%～95%病毒性脑膜炎是由哪种病毒引起（）
A.单纯疱疹病毒
B.巨细胞病毒
C.带状疱疹病毒
D.肠道病毒
E.腺病毒
