用所给词的适当形式填空
①I have two ____ (brother).
②There are two ____ (family) in the picture.
③ The old man has no ____ (son) or ____ (daughter).
④ My ____ (father) sister is my aunt.
⑤In the photo his mother's ____ (parent) are on the left.
测量液体密度的仪器叫密度计,将其插入被测液体中,待静止后直接读取液面处的刻度值(图甲).图乙和图丙的容器中是同一个自制的简易密度计,它是在木棒的一端缠绕一些铜丝做成的,将其放入盛有不同液体的两个烧杯中,它会竖直立在液体中,由图中现象可以判断( )
菜粉蝶等农业害虫对作物危害最严重的时期是 ( )
图《变与不变》中, 不变的真正寓意是( )