为你解答.
Some people have to （stand） when all the seats are full.(根据划线部分提问)
What do some people have to do when all the seats are full?
当座位全坐满时,有些人不得不做什么?some用在肯定句，any用在否定句和疑问句一般情况下是这样，但这里用any不合适。