以下哪些场所,不宜选择火焰探测器()。
A、可能发生无焰火灾
B、在火焰出现前有浓烟扩散
C、探测器的镜头易被污染
D、探测器的“视线”易被遮挡
参考答案:A, B, C, D
I _____ a book when it began to rain that evening.[ ]
A. read
B. have read
C. was reading
D. would read
零息债券