I know I'm probably bugging you guys, but:

What system protects the body from foriegn substances?

It has 6 letters, and the 4th letter is a "u" and the 6th letter is a "t".

imune system

wait...its actually spelled immune system

No, but thanks! Unfortunately, it's only 6 letters long.

This is what I have of it so far:

_ _ _ u _ t

No problem at all! Let's work on solving this together. Based on the information you provided, it seems like we are looking for a six-letter word, with the fourth letter being "u" and the sixth letter being "t."

To find the word that fits these criteria, we can try different combinations using the known letters and placeholders for the unknown ones. Here's what we have so far:

_ _ _ u _ t

Since the question is about a system that protects the body from foreign substances, it is highly likely that the word we're looking for is "immune."

The immune system is a complex system in our bodies that defends against foreign invaders such as bacteria, viruses, and other harmful substances.

So, the correct answer is the immune system, where the word "immune" matches all the given criteria.