C) Celebrate. This would make better sense, since it isn't having a claim to recognize something when it already is a holiday. Observing something would simply be to inspect. Mark is definitely not your answer and you should know that the last ones available aren't reasonable! So the answer is C)
It's really important to know your audience when you start writing something. For example, if you want to write a dystopian novel, usually teens and young adults read such books, so you want to modify your novel and theme a bit to better suit their interest and understanding. You need to decide on which group of readers you want to write for so that you can adjust themes, motifs, characters, etc.
The repitition of these words continue to enhance that something bad or abusive happened to a person, animal or living thing.