Go and make someone laugh — just might help them live longer.
A. it
B. which
C. that
D. they
网友回答
(答案→)A. it
B. which
C. that
D. they
解析：考察代词用法。因为句中用的是破折号，所以排除B。It 代指上文提到的同一个事物。此处代指的就是go and make someone laugh， that 代指可数名词单数，或者不可数名词，特指。与前文提到的东西是同一类而不是同一个。They代指的是可数名词复数。