A. Have been B. Are being C. Had being - should be 'had been'. D. Were been When you have a main and subordinate clause in 'think/assume/hope/etc that ...' form with the main clause verb in the past tense, the sub-clause verb is back-shifted, so it should be 'had been' instead of 'have been'. Plus, all except A make a grammatically wrong construct. 'are being paying', 'had being', 'were been' are ALWAYS wrong with absolutely no exception.

Had been

Hi! I think that the only suitable answer would be "A". Reason: HAVE BEEN is used when you talk about something that started in the past tense and normally doesn't have a determinated time to finish. In your sentence you are talking about something that is going to last until the end of the year (it can be any day or moment like november or dezember, you know?) It is an indeterminated moment. ARE BEING is only present tense, not past tense. So, there is no reason to use it in your sentence. HAD BEING is incorrect English. WERE BEEN is incorrect English, too. Good studies!

I assumed you were going to pay for the repairs until the end of the year.