Which of the following italicized parts DOESNT indicate reason？A．Something fell in, for I

Which of the following italicized parts DOESNT indicate reason？

A．Something fell in, for I heard a splash.

B．Much as I love sports, I prefer to stay at home on Sunday.

C．He saw her, as they were both getting on the bus.

D．Now that I"m here, I"d better stay.

请帮忙给出正确答案和分析，谢谢！