B>it's because it states there is only one.
The suitors must string Odysseus's hunting now that he knew how to string. After that, they have to shoot an arrow through twelve axe handles. If they completed this, they would win her hand in marriage.
Entertaining
At your aunt's retirement party, you would want to give a fun, entertaining speech incorportating a story about your aunt.
At a retirement party, you don't need to persuade anyone to do anything, since you knew about the retirement party, you would have planned a speech (so it would not be extemporanous and done spontasiously) and there's no need to inform anyone of anything at a retirement party.