同义句转换

1. I think he is not so tall as his father.

I think his father is _____ ____ him.

2. I like dolphins because they're cleverer than any other animal.

I like dolphins because they're    ___ ____ animal.

3. This road is 10 kilometers long. That road is 300 meters long.

This road is ____ ____ ____ that one.

4. I'll stay here instead of going there with you,

I won't go there with you. I'll stay here ____.

5. This passage is short and there are no new words in it, but it is difficult to understand.

____ this passage is short and there are no new words in it, ____ it is difficult to understand.

背景材料：白血病又名血癌，是一种高死亡率的病症，在我国的发病率为2.76×10-5。在儿童的恶性肿瘤发病率中，白血病居第一位。白血病是由于造血干细胞增殖分化异常而引起的恶性增殖性疾病，它不仅影响骨髓及整个造血系统，还侵犯身体其他器官。目前能根治白血病的唯一方法是进行造血干细胞移植。根据以上材料回答下列问题：

当前治疗白血病的首选方法是。但没有亲缘关系的骨髓中其配型相合的仅有，在同胞兄弟姐妹中也仅有25%的概率，试简述其原因。