Answer:
It is asking you to write what you learned from a certain experiance, like "This experiance has taught me that lying leads to consequences." Or something like that. Also In your first paragraph, it says, "'because when I was younger" You could combine it with "I believe that lying is bad" Instead you could say, " I believe that lying is bad, for example when I was younger..."
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)