Answer:
A serious poem written to express strong emotion is called an ode.
Step-by-step explanation:
An ode is a type of poem in which a strong feeling or emotion is expressed toward someone or something. That definition helps us conclude that an ode is the best option for this question.
A limerick is a humorous type of poem, not a serious one, consisting of five lines. An epic poem is usually very long, and it tells readers about the heroic acts of its characters. A sonnet has a very specific form and, even though it can express emotion, it is not necessarily serious.