In "the carp" by yun wang, the use of the carp to represent something deeper is an example of synecdoche. the carp is used to represent the pain and injustice of her father’s imprisonment.
Its what happened soto speak in areas where currency was unheard of you gave work/life for work
We don't have any proof that he or his own child got poliomyelitis as an infant. Also, this disease has been a serious issue <em>before </em>he became a doctor, so 2 is out also.
This only leaves one answer left. =)