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Answer: CSet 2: Words in Context (Beginner)
Explanation
PASSAGE
The scientist's _____ observation led to a breakthrough in cancer research.
Which choice completes the text with the most logical and precise word or phrase?
A. careless
B. accidental
C. careful✓ Correct
D. rushed
Detailed Answer Explanation
Choice C is the best answer. "Careful" is correct because it means "done with attention and thought." The context clues in the passage indicate that this meaning best completes the sentence logically.
Why others are wrong: A ("Careless" means "done without attention," which doesn't fit the context.), B ("Accidental" means "happening by chance," which doesn't fit the context.), D ("Rushed" means "done too quickly," which doesn't fit the context.).