下图中①~④表示人体与外界进行气体交换的过程,下列相关叙述正确的是( )
A:①过程引起有节律的呼吸运动
B:②过程的进行依赖于胸廓容积的变化
C:长期缺铁会影响③过程中气体的运输
D:②④过程均使血液由动脉血变为静脉血
铁路转弯处的弯道半径r是根据地形决定的.弯道处要求外轨比内轨高,其内外轨高度差h的设计不仅与r有关,还与火车在弯道上的行驶速率v有关.下列说法正确的是( )
已知a+2ii5=b+i,a,b∈R,其中i为虚数单位,则a+b=( )
用括号内所给单词的适当形式填空(1)What a____ (please) it is for me to play the piano with you!(2)Mother asked the Greens to help____(they) to some pears.(3)Tim sings even____ (badly) than before.(4)He felt____ (true) sorry for what he said.(5)____ (clean) work is to make our city clean.
—Tina didn't go to school yesterday, did she?
— . Bcause she was badly ill.