Correct Answer: law-abiding

Solution : The correct choice will be the fourth option.

Obsequious refers to someone who is excessively obedient or attentive, often in a servile or ingratiating manner.

Law-abiding describes a person, group, or entity that adheres to and follows the laws and regulations of a given jurisdiction.

The meanings of the other options are:

Mischievous: It refers to a person, behaviour, or action that is playful, teasing, or mildly naughty but not intended to cause serious harm or damage.

Defiant: It refers to a disposition or attitude characterised by a refusal to yield to or comply with authority, expectations, or established norms.

Headstrong: It describes a person who is determined to have their way, often stubbornly or willfully.

Therefore, the most appropriate synonym to replace the italicized word "obsequious" is "law-abiding".