正确答案: D

种间竟争

题目：在自然状态下，某一桦树林中出现了云杉树苗，云杉长大后，高度超过桦树林。桦树不如云杉耐阴，而逐渐减少，最终形成以云杉为主的树林，这种现象是

解析：D

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学习资料的答案和解析：

[单选题]--My mother is preparing my favorite dishes, Go with me and have a taste, okay?--_______. And I’ll be glad to meet your parents.

I think so

[单选题]下列词语中，字形和加点字的读音全部正确的一项是

天涯海角 丢三落四 提防（dī） 道行很高（héng）

解析：【解析】（A鞠—掬；B“纤”读xiān；D肩—奸）

[单选题]22 The workers——the glasses and marked on each box” This Side UP”

packed

[单选题]41________

announced

解析：

本句句意应为“典礼的主持人清晰地大声宣布下面表演的是我们班。”表示“宣布”用announced。

[单选题]BBoiler rooms are often dirty and steamy, but this one is el.ean and cool. Fox Point is a very new47-unit living building in South Bronx, one of the city’s poorest areas. Two-thirds of the people living there are formerly (以前) homeless people, whose rent is paid by the government. The rest are low-income families. The boiler room has special equipment, which produces energy for electricity and heat. It reuses heat that would otherwise be lost to the air, reducing carbon emissions(碳排放)while also cutting costs.

To show how the environment-friendly building works.

[单选题]决定受精亲和或不亲和的物质是花粉壁和柱头表面的( )。

蛋白质