The primary purpose of heart valves is to prevent blood from flowing backward.

pump blood backward.

exchange carbon dioxide for oxygen.

protect the heart from trauma.

I’ve personally felt invisible all my life, especially when a friend turned out to be fake and didn’t seem to take any type of interest in what i said or any type of input i said. being invisible is a terrifying feeling to experience due to the fact you feel like no one sees you and just sees you (sorry if that doesn’t make sense). it’s like a deep emptiness that no one can fill, just you; you have to fix that emptiness by yourself and you don’t really want , or in some cases want to be invisible. i can see many invisible people when they intentionally stay away from people that can potentially hurt them in any way. also, when a person intentionally breaks off a connection so they aren’t seen by people.hope it

The answer would be a (carbohydrates)