The answer is most likely "Is"
Answer: It can affect brain development, leading to learning and behavior problems.
Explanation:
Answer: So, your main idea or thesis here that you are talking about in this paragraph would be your goal to acheive things out of your own comfort zone.
However, more specifically you could make your thesis on either your desire to make new friendships or relationships / or you could make your thesis be about your desire to experience new situations that are out of your comfort zone..
Hope this helps some!
Kahi jeeb llakeee back he. a a e jjnj vfbea naj