I. Complete the following sentences with the best choice.
1. It never ______ my mind that the clue to the problem lies in such a simple experiment.
A. entered
B. occurred
C. happened
D. meant
2. A series of meetings ______ about the best way to market the new product to foreign countries.
A. are held
B. were held
C. was held
D. have been held
1. It never ______ my mind that the clue to the problem lies in such a simple experiment.
A. entered
B. occurred
C. happened
D. meant
2. A series of meetings ______ about the best way to market the new product to foreign countries.
A. are held
B. were held
C. was held
D. have been held

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