"Does she want to eat lamb or beef?"
This is the traditional writing system of Chinese. Still in use, but we generally prefer Simplified version. My school teaches simplified version.
What is the problem with saying 他想吃牛肉还是羊肉 ——— 一样的意思呀！ It delivers the same meaning !!!
No, 还是 already implies the question. In a statement you would say 或者 huòzhě.
It says incorrect because I didn't add 想. But doesn't this lesson teach that 想 is not necessary?