The correct option is B Since
A subordinate clause ("You love music") depends on the main clause ("we will take you to a concert for your birthday") for its full meaning. To combine these two, a subordinating conjunction is used. The subordinate clause here states the cause 'love for music' for which the action in the main clause 'going to the concert' takes place. 'Although' is used when the sentence is contrast-related, when the clauses in a sentence have contrast or opposite meanings, for example, 'Although you love music, we cannot take you to the concert for your birthday'. Since the given sentence is not contrast-related, but cause-related, option D is incorrect. 'Since' is used for cause-related sentences, and is appropriate here as it states the cause 'love for music', hence option B is correct. 'Yet' is a coordinating conjunction that combines two independent sentences as one, these sentences are complete on their own, hence do not depend on each other. As the given sentence does not have both independent clauses, one of them is dependent, hence 'yet' will not be used, and option A is incorrect. 'After' is used for time-related sentences, and the given sentence does not focus on time, but cause-and-effect. Hence, option C is incorrect.