<span>Él es un compañero de clase is the right answer. The 1st sentence is ella but </span>compañero should be compañera. In the second one ella should not have an accent mark and in the last one el doesn't match with una.
For Tener: ¿Tienes las respuestas para la tarea de matemáticas?
For Estar: ¿Estas en la casa de (insert any name)?
Can’t think of one for ser but hope these two help
1. she is swimming
2. we are playing
3. i am running
4. they are walking
