The correct option is
D Always
In order to fill in the blank with an adverb of time, let's understand what 'Adverb of time' is. Adverbs of time explain when the actions take/took/will take place. For example, He played cricket yesterday.' Here, 'yesterday' explains when the subject 'played cricket.'
NOTE: The word 'Fridays' explains that the question is a general idea. Without an adverb, we can understand that the question is if the subject often/regularly goes to the cinema on Fridays.
Option A - 'Seldom' is an adverb, which means 'rarely'. 'Do you rarely/seldom go to the cinema on Fridays?' is grammatically incorrect as 'seldom' is used for negative ideas and sentences, whereas the given question is positive. Hence, option A is incorrect.
Option B - 'Hardly' is an adverb, which means 'barely', it is a negative word and hence, we can't use it here. Thus option B is incorrect.
Option D - 'Infrequently' is an adverb which means 'not so often'. As this a negative word, we can't use it here. Hence, option D is incorrect.
Option C - 'Always' is an adverb which means 'at all times'. As it is a positive word, we can use it in a positive question. Hence, option C is the correct answer.
'Do you always go to the cinema on Fridays?'