题干

下图为人体某早期胚胎细胞所经历的生长发育阶段示意图,图中甲、乙为两个阶段的细胞,a、b表示发育变化的模式过程。下列叙述正确的是 (     )

①a过程有可能发生基因突变
② 乙细胞不同基因重组导致b过程产生不同细胞
③ 上皮细胞与甲细胞的遗传物质相同,因此它们的细胞分化能力应该相同
④ 甲细胞中的蛋白质与神经细胞中的蛋白质不完全相同

A:①④

B:③④

C:①②

D:②③④

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    Everything you do to protect the planet helps all living things, including humpbacks(座头鲸)and other species of whales that live in oceans worldwide. And yes-just one kid, like you, can make a difference.____

    Don't litter. Rubbish thrown away carelessly outside often washes into storm drains(排水沟), which empty into rivers and eventually flow to the oceans.____including whales.

    Say, “No bag, thank you.” Whether you're buying toys, snacks, or clothes, tell the checkout person you don't need a bag.____you'll help reduce the 100 million plastic bags that each year block sewers(下水道), and get swallowed by whales, sea turtles, and other wild life.

    Plant a tree.____They produce oxygen and absorb carbon dioxide(二氧化碳), a gas that animals, including humans, produce naturally as they breathe. But because carbon dioxide also comes from cars and factories, there is too much of it in the atmosphere, which is contributing to global warming. If everyone planted one tree, those trees would remove a large amount of carbon dioxide from the atmosphere.

    ____Every time you leave a room for more than a minute, turn off the light you're using. In this way, you save energy and keep greenhouse gases out of the atmosphere.

    Try the family challenge! Many streams and rivers are polluted and littered with rubbish. You and your family can help preserve the waterways by joining others in your community to pick up rubbish.

A.Trees help clean the air we breathe

B.Turn off the light

C.Avoid driving cars

D.By carrying your own reusable bag

E.Treat them like friends

F.Here are ideas for easy small things you can do

G.Pollution is a growing problem for all the Earth's oceans and its wildlife