The American Navy experiment measured the ocean with

• A、heat

• B、light

• C、rope

• D、sound

Task 2

20. It is popularly believed that all research needs ca    

21. One should make sure the research is____

22. It is as difficult to solve a useful problem as to    

23. One may need some simple equipment to overcome    

24. Not many people realize that it is difficult to    

25. Failures in research    

A. happen very often

B. worth doing

C. do something new

D. lose one's patience

E. solve a useless one

F. expensive scientific equipment

G. the major difficulties in research

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