用所给词的适当形式填空。

1. Our headmaster invited a singer ________ (sing) for us this morning.

2. I _______ (clean) my room at 9:00 last Sunday.

3. They can do that thing by ________ (they).

4. I think _______ (predict) the future is a bit difficult.

5. The teacher told us that light ________ (travel) much faster than sound.

《七略》是我国第一部综合性的系统反映国家藏书的分类目录，又是我国最早的一部图书分类法，成书于公元前6年，根据当时的国家藏书编制而成，其作者是刘歆。请谈谈《七略》的基本类目有哪些？