A:k<12
B:k﹤1且k≠0
C:-12≤k<12
D:-12≤k<12且k≠0
蒸汽机发明和使用后,在欧洲出现了一大批相对集中的工业城市,所以有人说:“蒸汽机是工业城市之母。”这是因为( )
— Lily, look, a crowd of birds are flying to our small yard.
— Just now, I threw some bread in the yard. They have come here for the food.
将某植物放置在黑暗处一昼夜后,选取一叶片按图甲处理,照光几小时后,摘下叶片,去掉锡箔,经脱色、漂洗再碘液处理,结果如图乙所示.下列分析中错误的是( )