问题补充：
If their marketing plans succeed, they their sales by 20 percent.
A. will increase
B. have been increasing
C. have increased
D. would be increasing
答案：
(答案→)A. will increase
B. have been increasing
C. have increased
D. would be increasing
解析：题意是“要是他们的市场计划成功了，他们将增加20%的销售额”。从句是一般现在时表将来，主句常用一般将来时或情态动词can/may + 动词原形。如：If we get up early tomorrow morning, we may/can see the sunrise.
