The term "invariable" refers to something that does not vary or change. Among the provided options, "constant" best expresses the meaning of "invariable," indicating a state of consistency and lack of variation.

The term "dulcet" is used to describe something that is sweet, soothing, or melodious, especially when referring to sounds or tones. Among the provided options, "sweet" best expresses the meaning of "dulcet," indicating a pleasant and harmonious quality.

The term "innocuous" refers to something that is harmless, inoffensive, or unlikely to cause harm. Among the provided options, "harmless" best expresses the meaning of "innocuous," as it denotes the absence of harm or danger.

The term "deposition" typically refers to the act of removing someone from a position of authority, especially in a legal or political context. "Impeachment" aligns closely with this meaning, as it involves charging a public official with misconduct and potentially removing them from office. Therefore, among the given options, "impeachment" best expresses the meaning of "deposition."

The word "petulant" is used to describe someone who is easily irritated, annoyed, or displays sudden, impatient irritation. Among the provided options, "peevish" is the term that best expresses the meaning of "petulant," as it denotes a disposition prone to being irritable or easily annoyed.

The word "grandeur" refers to the quality or state of being grand, impressive, or magnificent, often in terms of beauty or scale. Among the given options, "magnificence" best expresses the meaning of "grandeur" as it signifies a quality of greatness, splendor, or impressive appearance.

The word "obnoxious" describes something or someone that is extremely unpleasant, offensive, or annoying. Among the given options, "disgusting" best expresses the meaning of "obnoxious," as it denotes something highly offensive or repulsive.