在下列各句的空白处填入一个适当的词,使句子意思完整、语法正确。
1. He isn't interested in modern history. Instead, he is interested in a_________ history.
2. An i__________ is a piece of land in the middle of the sea.
3. Thanks to the teacher's help, I have made great p________ in learning English.
4. There is no noise. It is a p________ place. You can think about something carefully.
5. He is so serious that I f______ to talk with him.