I was making a Yahoo account so I can email my teacher my assignment, and then it asked for my cell number. I'm 16 year old and I don't have a cellphone. I won’t see my teacher for 3 weeks because we’re on break. How can I bypass this?
It's a measure to make it harder for spammers to create throwaway accounts. Unfortunately, like many security measures, it inconveniences innocent users more than the bad guys it's trying to stop.
There are lots of free webmail services out there. Certainly there's some that won't bug you for a cell phone number. (Have a look at Computers: Internet: E-mail: Free: Web-Based for some, or perhaps even http://alternativeto.net/software/yahoo-mail).