Given the task definition and input, reply with output. In this task, you are given a context paragraph of the tweet and question. Your task is to generate right answer of given question based on given context tweet paragraph.

Context: Merry Christmas to all. A Pagan holiday (BC) becomes a Religious holiday (AD). Which then becomes a Shopping holiday (USA). Neil deGrasse Tyson (@neiltyson) December 25, 2014 Question: what is neil degrasse tyson celebrating?
christmas