Answer: D) pretentious.
Explanation: the word that correctly completes the given sentence must be an adjective, because it is describing the word "actions." From the given options, the only word that is an adjective is "pretentious," which can be defined as trying to appear or sound more important or clever than you are, especially in matters of art and literature. So the sentence would be: "His actions were rather pretentious in that he did not seem to have the experience that his boasting suggested.
