主语从句是复合句中用来充当主语的句子。以下是一些主语从句的例句：
1. That he finished writing the composition in such a short time surprised us all.
2. What is needed for the space trip is careful preparation.
3. Whether wild life can be well protected is of great importance.
4. Who will go makes no differences.
5. Why dinosaurs died out remains a puzzle.
6. Which kind of food is the best is still not certain.
7. That he is still alive is a wonder.
8. That we shall be late is certain.
9. That he should have ignored the working class was natural.
10. What he said is true.
11. Whether we will win the game is uncertain.
12. Whoever comes late will be punished.
13. If it rains tomorrow, we will stay at home.
14. No one can refute the basic fact that unemployment is an important reason for city crime.
这些例句展示了如何使用不同的引导词（如that, what, whether, who, when, why等）来构造主语从句，并且说明了主语从句在句子中充当的成分。希望这些例句能帮助你更好地理解主语从句的用法。