根据下列句子所给汉语意思，写出空缺处各单词的正确形式。

1. _______(事实上), on second thought, I don't think I want to go out tonight.

2. He caught a cold yesterday and ______(遭受) from a headache last night.

3. He was too ________(顽固的) to admit that he was wrong.

4. It is surprising that he can speak _______(流利的) English after such a short time in England.

5. Mr. Wang went back to work after he fully ________(恢复) from the operation.

如图是人体内血液与组织细胞之间的气体交换示意图。请据图回答下列问题：

（1）图中血管是            血管，你判断的理由是                            。

（2）图中X表示的气体是              ，Y表示的气体是               。