The given word 'agility' means ability to move. Ex: Her mind showed an enormous amount of agility in solving the problem.
inertness - Lack of activity or exertion. liveliness - the quality of being outgoing, energetic, and enthusiastic. fleetness - the ability to run or move quickly. adroitness - cleverness or skill. The most appropriate antonym of the out of the given options is 'inertness' i.e 1st option.