21. The Thinking Machine ________ in solving the mystery of the silver box.
A. persisted
B. achieved
C. managed
D. succeeded
22. Life is not merely ________, but the enjoyment of health.
A. living
B. alive
C. lively
D. liveable
23. Most of the men working in the factory were farmers ________.
A. formally
B. formerly
C. early
D. firstly
24. A successful man is ________ who has the opportunity and takes it.
A. person
B. anyone
C. some
D. one
