Since then the population of Londonby almost 50,000 a year—an increase largely fuelled by

Since then the population of London by almost 50,000 a year—an increase largely fuelled by immigration.
A. has risen　
B. have risen
C. rises　
D. rise

(答案→)A. has risen　B. have risenC. rises　D. rise解析：考查时态和主谓一致。population(集合名词)应看成一个整体，谓语动词用单数形式；句首的Since then表明谓语动词应用现在完成时态。自那时起，伦敦的人口每年几乎增长50 000人，主要是由于移民的涌入。

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