The correct option is
A Dormant
'Latent' means present but needing particular conditions to become active, obvious or completely developed.
Option B - 'Apparent' means able to be seen or understood. Thus option B is incorrect.
Option C - 'Lethargic' means having little energy; feeling unwilling and unable to do anything. Thus option C is incorrect.
Option D - 'Prompt' means to cause or to make something happen. Thus option D is incorrect.
Option A - 'Dormant' means something that is not active or growing but has the ability to be active at a later time. Thus option A is the correct answer.
'Latent - Dormant'