Hola Annie

Looking at your recent tests I can see that you are probably referring to these two questions.

One has the word "Hugo" so here you need "o" in front: 

1. ¿Cómo se llama tu novio, Horacio ___ Hugo?

2. ¿Qué prefieres, apartamento ___ hotel?

One has the word "Hugo" so here you need "o" in front: "Horacio o Hugo"

You need o, not u because it is "Hu-", not Ho-, so we still use the usual conjunction "o". (you marked the -u in this case)

Two  has the word "hotel", starting with ho-, so here you do need the conjunction u, not o:

"apartamento u hotel"

In the lesson we say that if the conjunction is needed before a word starting with o- or ho- you need to change the conjunction from o to u (to make it easier to pronounce)

I hope it clarifies it.

Saludos

Inma