题干
The students were studying in____________classroom when, all of ____________sudden,the lights went out.
A：不填;不填
B：a;the
C：the;a
D：the；不填
答案(点此获取答案解析）
C
A：不填;不填
B：a;the
C：the;a
D：the；不填
不正确的是 （ ）