Choose the word that best complete the sentence HELP!!

Which verb or verb phrase signals an inappropriate shift in mood. a) will you let b) should first change c) must attend d) will be served

This is a set of words that begins with a preposition.

Power going out story i need with a plot and the starting point is you wake up late, the power is out, and yeah. plz try to make it non complex since i have to write it in spanish