"Envious" means jealous; Erroneous means mistaken; Excessive means too much; Sociable means outgoing; and Incessant means continual.

Someone who is "optimistic" looks at things positively or thinks that good things will happen in the future. We need to find a word with a positive meaning. We can rule out the word "gloomy" as it is the only word with a negative meaning. Out of the remaining words, "hopeful" means full of the idea that good things will happen, "heartfelt" means sincere, "good" means right or proper, and "nice" means kind. The last three words can be characteristics of a person who is optimistic, but are not themselves synonyms of the word "optimistic." "Hopeful" is the best choice. 

The best choice is "mournful" as something that is "elegiac" is mournful or expresses sorrow. The remaining answer choices are simply other types of emotions. The only one which might be somewhat related is the word "worrisome" which means causing worry, but "mournful" is closer in meaning to "elegiac" than is "worrisome."

"Bellicose" and "belligerent" share a root and are synonymous. Both adjectives refer to demonstrating aggression. The other words are antonyms to "bellicose." 

"Distraught" and "fraught" are synonyms describing a frustrated emotional state. The other words do not share this meaning. "Infected" and "infectious" refer to the state of being infected with a disease and the property of being transmissible to others (usually of a disease or emotional state, like laughter) respectively.

"Infuriated" and "enraged" are synonymous adjectives describing someone who feels severe anger. "Pleased" and "humored" are antonyms. "Aggravated" and "annoyed" are synonymous with each other and may refer to someone who is irritated but not necessarily extremely angry.

"Flustered" and "discombobulated" are synonymous; they refer to someone who is frustrated with a situation. The other words do not come close to being synonyms. In fact, "thoughtful," "logical," "alert," and "clearheaded" are actually all somewhat related to each other. The one word that really stands out is "discombobulated."

"Leery" means cautious and wary. "Affable" means friendly or amiable. "Magnanimous" is a synonym for generous, as is "munificent." "Congenial" means personable, hospitable, and genial.

"Rash" means hasty and reckless. "Direct" and "indirect" are antonyms, as are "cheerful" and "unhappy." "Iconic" means classic. "Aggressive" means antagonistic and hostile.

"Distraught" means distressed and upset. "Bashful" means shy, and "bewildered" means confused or confounded. "Dismal" means glum and dreary, and "grim" means dark, stern, or dire, depending on context.