已知:Ⅰ.RCHO+R′CH2CHO →Δ稀氢氧化钠 +H2O(R、R′表示烃基或氢)
Ⅱ.醛与二元醇(如:乙二醇)可生成环状缩醛:
下列说法正确的是( )
下列生态系统中自动调节能力最强的是( )
如图是我国某地的一个人工农业生态系统模式图,它利用鸭旺盛的杂食性,吃掉稻田里的杂草和害虫,用水稻养猪、养鸭,水稻的秸秆可以培育蘑菇、生产沼气,猪鸭粪、沼渣肥田.请据图分析回答:
We have a big playground in our school .We all like to 1 games 2 after school .It's Friday .We have only two classes 3 the afternoon . 4 school is over(结束的),a lot of students go to the playground quickly. The boys of Grade Two often 5 soccer. The girls like 6 them playing .Soccer is their favorite sport . Their teacher Mr Li also 7 football. Li Ming , Li Lei and Wei Fang are students of Grade One .They sometimes play 8 the students of Class Two. It’s half past five 9 . It's time 10dinner . My father is waiting for me at the school gate .