Why do teenagers lie?

I took a deep breath and let it out. “Mom I could have been pregnant, but I’m not.”
Mom backed away from table and screamed so loud I thought the roof was going cave in on us. “What do you mean you could have been pregnant?”
My brother came yelling as he entered into the kitchen from his bedroom him and his wife were renting from my parents. He yelled so loud the neighbors had to think someone was being killed. “Is every thing okay?” I began to cry with tears that made me feel like I was becoming a puddle of water. My mother looked at my brother and said, “Elizabeth could have been pregnant.” I told everyone the story of going for the pregnancy test. My mom yelled out over and over. “What… what. That boy Paul has a lot to answer to me.” I sat with a relief of knowing I got one lie out of the way. Even though I knew it made look weak to have done what I did with Paul.