The correct option is D funny as a clown
A simile is a figure of speech that presents the likeness between two
unlikely things and contains the words 'like' or 'as'. For example, as
smooth as butter, light like a feather and so on. In the given pair of sentences, the uncle is compared with a clown, a likeness is presented due to both being funny and entertaining. Hence the phrase "funny as a clown" is a simile and option D is correct. "Your uncle" is the subject of the first sentence and does not function as a simile, hence option A is incorrect. "Was" is a verb in the past tense, it does not perform as a simile. "Life of the party" is a noun phrase made up of a noun + preposition + article + noun; hence options B and C are incorrect.