here are a few reasons:
1）为什么非得用英文？

2）英文用了也就用了，为什么口气要那么的盛气凌人？一副高高在上的样子，好像蔑视任何美丽的和正常的东西。你到底想要说什么？

3）要是自己真NB盛气凌人也就原谅你了，几个问题问的怎么就感觉这么欠扁呢？这都是什么乱七八糟的东西啊？觉得你自己观察仔细，容易发现大自然中的种种问题？说实话上华新这么久也没看到哪个帖子让我这么的气，这么白痴的一对问题一般我也懒得理。也可能是因为刚才考试考的郁闷了心里不痛快，今天还真就想好好教育教育你！

1) Why some leaves are yellow but others are green?

Ans: Some tress never turn yellow even in winter, and even if they do, it's not to say 1,2,3 all the leaves will turn yellow at the same time!

2) Why are there green trees when it is in winter?

Ans: See above answer. And sometimes, snowing is not a definite indicator of winter. Occasionally, it also snow in late autumn or early spring, like Oct or April.

3) Why in winter there are roses?

Ans: See above answer.

4) Why are the fallen leaves ON the snow layer instead of below 'em?

Ans: sometimes, leaves fall after snowing.

5) Why are the leaves not rotten when the snow melts?

Ans: the rotten process is not shown in the pictures.

6) Why are the leaves not drooping when there are snow on 'em?

Ans: "Drooping"? or do you mean dropping? Refer to above answers. And some trees do have higher tolerance level to the coldness of winter.

7) Why are there snow on the car and buses when there is no parking slot nearby?

Ans: Not all cars or buses are parked on parking slots. Yes, i know you might going to say "see the ugly Chinese!", but hey, the lack of parking slot might be due to fast growing economy. Moreover, despite of such fact, we still enjoy the beautiful snow scenes.

8) Assume wind comes from the north, and snow fall on the north side of the trees, why does the sun shine from north also? ;)

Ans: What has the direction of sunshine to do with the direction of the wind? You think there are only wind breeze from the north in winter?

第一次在这里说了这么多英文，对不起大家了。就是看不上那种本来自己没什么水平就喜欢献的！用俺们那块儿的话说，这就叫“的色！”