紫外线对人体的危害主要是造成皮肤和眼睛的伤害,其引起的原因是紫外线的()。
A.热作用
B.光化学作用
C.电离作用
参考答案:B
短语:从方框中选择适当的短语,并用其适当的形式填空,有两个多余项。
(每题1分,共5分)
1. ________________ you’ve got a chance, you had better make full use of it.
2. I think the photos can ________ us ________ the days we spent together in the country.
3. When they crossed the Rocky Mountains, they managed to _____________ some mountain goats.
4. He wrote a long moving poem ________________ those who died in the war.
5. It is not polite to ____________ other people.
在有n个结点的二叉树的llink-rlink法存储表示中,n个结点所含有的2n个指针中,必有 【2】 个为空指针。