16. Science can penetrate many of nature’s ______________. (mystery)
17. My watch had ______________ disappeared. (mystery)
18. I’m doing ______________ , biology and chemistry. (physics)
19. Faraday was known to be an outstanding ______________. (physics)
20. She listens to classical music for ______________. (relax)
21. It was so ______________ to be among old friends. (relax)
22. There’ll be time to ______________ when you’ve finished your work. (relax)