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While he was investigating ways to improve the telescope Newton made ______ discovery which completely changed ______ man's understanding of color.

A. a ; /
B. a ; the
C. /; the
D. the ; a
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单项选择题When he left ______ college, he got a job as ______ reporter in a newspaper office.

A. /; a
B. /; the
C. a the
D. the; the

单项选择题______ recent report stated that the number of Spanish speakers in the U. S . would be higher than the number of English speaker by ______ year 2090.

A. A; the
B. A; /
C. The ; /
D. The; a