1.______the students think it their duty to study hard has laid the foundation for the university's high reputation.

2. It has always puzzled me______ theold man tied a red silk ribbon on the young tree in his courtyard.

4. The question is______ can be put into practice.

6. ______ was to return to school.

8. ______ unstable and explodes as a supernova is known.

______the students think it their duty to study hard has laid the foundation for the university's high reputation.