What do I tell her?

My dad came into my room to check some settings on my PC, one of the settings linked to opera GX, where I forgot to close a tab, so I js pressed alt f4 a few times. Dad kept trying to open the link, so I js turned everything off at the plug. Parents took away monitor, but I cleared history by linking to TV. Now mum's trying to get me to tell her what I was hiding. I need yall to help me what do I say so I had a reason to hide it without it being illegal and having it seem logical. Please guys I'm begging you all 🙏