Some cats will meow a lot when they're left alone without another cat or human companion to be around.
Although some cats prefer to be alone so it can vary from cat to cat.
If your cat meows a lot when you leave him or her alone you can try leaving a radio on low volume in the house so the cat doesn't feel all alone.
You might also have to get the cat another cat to have as companionship to keep the cat from getting lonely and meowing a lot when you leave the cat alone if you don't already have another cat.