Answer:
Since you asked for a single word as an answer choice, then the word you want is 'Christmas.' It names a specific holiday.
You should know that technically, the word 'Sony' is a proper noun as it is the name of a specific corporation/brand -- BUT .... in this sentence it's being used as an adjective for the common noun 'television' rather than functioning as a stand-alone proper noun.
If you were to say that the man bought a Sony Bravia 55XE90, then THAT (Sony Bravia 55XE90) would be a proper noun - because it names a specific model of Sony televisions.
Step-by-step explanation:
A proper noun names a specific item and begins with a capital letter no matter where it occurs in a sentence.