Why the downvotes? Schools in lots of places don't teach LGBT+ vocabulary and not everyone is interested enough to look it up. Many have never needed to answer anything other than "male/female/other" for gender, and very few people use the word "cis" to identify themselves, so it's OK to not know ithe term.

Edit: my school was rather progressive but I still can't remember being taught the term “cis” in sex ed at 12 years old and I only found out when I started seeing LGBT+ memes online and became an ally 5 years later.

Another reason why the poll I suggested in the previous comment is better.