Answer:
We must select the things you can do in Mexico, let's analyze all of them and see which ones are correct.
-see a cactus; You can see lots of cactus in Mexico, there actually is a thing called the "Cactus Sanctuary", this is correct
-take pictures of wildlife: You can, maybe you should not use flash, but you can photograph the wildlife., this is correct
- snow ski: You will not see snow in Mexico, so this is incorrect.
- see a volcano: there are a lot of volcanos in Mexico, for example, one of the most known is Popocatépetl, so this is correct.
- learn about the ruins of indigenous people: even you may find tours, so this is correct.
- snorkel or dive and see fish in the ocean: As in most places with shores, you can do this.
sleigh ride: Again, there is no snow in Mexico, so this option is incorrect.
swim in freshwater pool: Of course, you can do it, this option is correct.