Select whichever preposition or determiner you consider the most appropriate for the blank space.
I'll be working on this report ______________ 10:30 p.m.

Correct option is C

The word that can be filled in the blank is ‘until’ to make the sentence grammatically and contextually correct.
· ‘Until’ is a preposition used to indicate up to a certain time or event. Grammatical rule involved: ‘Until’ denotes a point in time at which something will cease to happen.
· As per the context, the phrase ‘until 10:30 p.m.’ implies that the work will continue up to that time, hence it is the correct option.
Meanings of other given words:
· During: This preposition indicates a period of time in which something happens but does not specify an endpoint.
· Since: This preposition refers to a point in time from which something has been happening and does not fit here.
· In: This preposition indicates a position within something but does not relate to time duration in this context.
· Thus, all the other given words have different meanings and do not fit in the context of the sentence.