Answer : 4. "Gloomy"
Explanation :

Answer: D) Gloomy Explanation: The given words are related in a way that, an optimist is a person whose outlook is cheerful. Similarly, a pessimist is a person whose outlook is gloomy.   The answer is not (b) because a pessimist does not have to be mean. Options (c) and (a) are incorrect because neither words describe the outlook of a pessimist.   Hence, Optimist is to cheerful as Pessimist is to Gloomy.