Which of the Following Best Illustrates the Do-Good,feel-Good Phenomenon

Which of the following best illustrates the do-good,feel-good phenomenon?

A) finding money makes people more likely to give money
B) people are more likely to volunteer their time to help others after they succeed on a challenging task
C) donating a kidney to another person increases the donor's subjective well-being
D) picking up someone's dropped papers is more likely after people recall a happy event