. She is a kind-hearted woman and often has _____ mercy _____ people who are in trouble.

A．a; on

B．\; on

C．a; o

D．\; to

根据收付实现制原则，凡是不属于当期的收入和费用，即使款项已在当期收付，也不应当作为当期的收入和费用。