Their income increased by 21 percent over that of the previous year.
A.他们的收入比前年增加了21%。 B.他们的收入增加到前年的21%。 C.他们的收入比上一年增长了21%。正确答案C
Their income increased by 21 percent over that of the previous year.
A.他们的收入比前年增加了21%。 B.他们的收入增加到前年的21%。 C.他们的收入比上一年增长了21%。正确答案C