Vocabulary and Synonyms

Mortal refers to being subject to death or error; fallible is a synonym for being prone to error. While lethal is related to death, fallible is a more direct synonym for the human condition implied by mortal.

Rejoice means to feel or show great joy, which is captured by the word delight. Abundant and mistake are not synonyms.

Fumble means to search (for a thing) by feeling about awkwardly with the hands; grope clumsily. Hence, option 2.  

Erratic means having no fixed course or purpose; irregular; random; wandering; deviating from the normal, conventional, or customary course. Option 1 is nearest in meaning.  

Sanguine means cheerful and confident; optimistic; hopeful. On contrary, doubtful means 'in doubt; not clear or definite; ambiguous'.

Generally we seek opinion of the person who has 'vast and deep' knowledge. The sentence implies the same. Thus, 'comprehensive' is the right option as it means 'dealing with all or many of the relevant details; including much; inclusive'.

Verbose means using or containing too many words; wordy; long-winded; prolix. On contrary, 'concise' means brief and to the point; short and clear.

Alleviate means to make less hard to bear; lighten or relieve (pain, suffering, etc). Mitigate means the same.  

Ingenuous means frank; open; candid. Its opposite word is 'dishonest'.

Enthusiams is a positive connotation word. So we need a word with the same connotation. Contagious means spread by direct or indirect contact; communicable.  

Offense means the act of breaking a law; sin or crime; transgression; the act of creating resentment, hurt feelings, displeasure, etc. Thus, option 1.  

Meetle means quality of character or temperament; esp., high quality of character; spirit; courage; ardor. Thus, option 3.  

This is a composite word that means “an intellectually disordered man” (mad means intellectually disordered or insane).

This is a composite word that means “to clean without using water” (dry means without water (liquid)).

This is a composite word that means “a track laid for wheels to run on" (rail means a track for wheels).