下列新闻时事中,与第三次科技革命有关的是
①用QQ软件视频聊天②克隆羊“多利”诞生
③网络购物,网络就医④瓦特改良蒸汽机[ ]
A.②③④
B.①②③④
C.①②③
D.①②④
答案:C
—Did Linda see the traffic accident?
—No, no sooner ____ than it happened. [ ]
A. she had left
B. she left
C. did she leave
D. had she left
地下或半地下的酸碱罐的顶部不准站人。酸碱罐周围应设()及明显的标志。