Which line from Act II of The Importance of Being Earnest is a paradox?

From Act II of The Importance of Being Earnest, the line which is a paradox is "Well, one must be serious about something, if one wants to have any amusement in life."

Explanation:

A paradox is defined as a statement that contradicts itself. This statement performs it since at the beginning it seems to talk about something "serious" and how this can lead to "amusement in life." The adjective "serious" means not cheerful, while the noun 'amusement' refers to something enjoyable. So, if the first one is necessary to reach the second one, the statement contradicts itself, turning into a paradox.

a simple sentence must have at least one dependent clause.