The correct option is
B How often the action occurs
Adverbs give us different kinds of information about an action. Adverbs that describe
how an action occurs are called adverbs of
manner (for example, happily, easily, sadly. etc). Thus, option A is incorrect. Adverbs that describe
where the actions occurs are called adverbs of
place (for example, here, there, ahead, etc), making option D incorrect as well.
Adverbs that describe how often the action occurs are called adverbs of frequency (For example, frequently, sometimes, etc). It does not tell what kind of action occurs. Thus option C is wrong while option B is correct.