Q: In this task, you're given a context passage, followed by a question that needs to be answered. Based on the paragraph, you must write unambiguous answers to the questions and your answer must refer to a specific phrase from the paragraph. If multiple answers seem to exist, write the answer that is the most plausible.
I was having a birthday party and wanted to invite all my family and friends so I had to make invitations. I went to the store to pick out the prettiest invitations I could find. There was so many to chose from I had to narrow down my choice. After I picked out my favorite it was time to fill them out. When I got home I got the list I made of people to invite so I did not forget anyone. I got out my address book and found everyone's address to put on the envelope . After they were collected and wrote down on the invites it was time to get stamps. I got them out of the desk and began filling out the envelopes. After the envelopes were done I put the invitations in them, sealed the envelope, and put a stamp on the right corner.  I mailed out all the invitations and was excited for the party to come. 
Question: What was the occasion?
A:
Their birthday