A:蒸腾作用可以促进水分和矿质元素的吸收
B:叶绿素a都可以吸收光能并把光能转换成电能
C:被子植物个体发育可分为胚胎发育和胚后发育两个阶段
D:当土壤中缺乏矿质元素镁、钾时,其植物的老叶首先表现出缺乏症状
— What's up? You look _____ right now.
— I'm afraid to take the exam. I'll let my mother _____ if I can't pass it.
下列物体中不是声源的是( )