The correct answer is symbolism. The use of the carp to represent something deeper is an example of symbolism.
Remember, a symbol is an object that takes on a meaning other than its literal meaning.
In the poem, the carp is literally a fish that takes on a deeper meaning. Confucius named his son Carp, and his son died young. The speaker's father was imprisoned and beaten. Therefore, the carp represents sadness and pain.