"Mettle" is defined as strength of spirit, so "courage" is the best match. "Timidity," which means lack of courage, is the opposite.

"Calamity" is defined as catastrophe or disaster, so the best choice would be "catastrophe." "Boon," which means benefit or blessing, is an opposite.

A "mandate" is an order. The best choice is "decree" because it shares the same meaning. Considering the other choices, "day" is the period of time during which the sun is above the horizon, a "chronicle" is a record of events from start to finish, and "breach," when used as a noun, means an act of breaking a rule or agreement or a gap in a wall.

"Audio" is another word for sound. "Sound" is the best choice because it is a part of the definition of "audio." Considering the other options, an "audience" is a group of people who are watching or listening to a particular event, "audacious" means daring or reckless, and "wise" means characterized by having knowledge and good judgement.

The word "parity" means equality. "Equality" is the best choice as it is a part of the meaning of "parity." Considering the other options, "part" means a piece of something larger, a "problem" is a difficulty or a question to be solved, and "parched" means excessively dry or very thirsty.

An "obloquy" is abusive language aimed at a person or thing. The best choice is "censure," as it shares the same definition as "obloquy." Considering the other choices, "quiz" means an examination or test, "local" means having to do with or originating in a particular area, and "oblivious" means unknowing.

An "epidemic" is a widespread outbreak of a certain disease. Therefore, "outbreak" is the word most similar in meaning to "epidemic."

An "enigma" is a mystery or puzzle. For example, one might write, "No one is sure whether Bigfoot actually exists: it is quite the enigma." So, "mystery" is the correct answer.

"Ambiance" means the atmosphere of a place. So for example, one might say, “The quiet café had such a peaceful, serene ambiance.” So, because "atmosphere" is the answer choice closest in meaning to "ambiance," "atmosphere" is the correct answer. To help you, "opulence" means wealth and luxury, a "virtuoso" is someone who is highly skilled at something, often to do with music, and "stark" means barren, harsh, or bleak.

While "sway" can mean move back in forth rhythmically, it can also be used to mean convince or influence. So, "influence" is the correct answer. To help you, "imitate" means copy, "sublime" means perfect or great, and "recede" means retreat or move back. When used as an adjective, "elaborate" means complicated, and when used as a verb, "elaborate" means go into further detail about or make more complicated.