I'll be taking my holiday . . . . . . . . Christmas this year.

The correct preposition to use in this sentence is on. The sentence should read: "I'll be taking my holiday on Christmas this year." The preposition "on" is used to indicate a specific day or date when an event will happen.

The other options are not suitable in this context:
B. "in Christmas" (Incorrect)
C. "at Christmas" (Incorrect)
D. None of the above