关于这个课后题，让你选择互斥项目X和Y要选哪一个，答案是A我能理解。但是B好像也对，是不是因为A更优选？能否帮忙解释下？
A. Project Y has a lower profitability index than Project X.
B. Project X has both a shorter payback period and a shorter discounted payback period compared to Project Y.
C. Project Y has a lower internal rate of return than Project X.