The correct option is
A always
The question requires you to fill the blank with an adverb of frequency. Adverbs of frequency describe how often an action occurs. For example, frequently, often, sometimes, seldom, etc.
In the case of options B and C, the adverbs "seriously" and"badly" describe how or
in what manner the action occurs. For example, "He performed badly last year.". They are adverbs of
manner. Thus, options B and C are incorrect.
"Still" is an adverb of time. It is different from an adverb of frequency in that it tells us when an action occurs (example, yesterday, later, now). The adverb "still" describes when the action occurs. i.e., that the action is occurring even now. It is thus an adverb of time, making option D incorrect.
In option A, "always" indicates how often the action of "listening to music" occurs - that it occurs repeatedly. Therefore, option A is the correct adverb of frequency.