I am guessing! but I would answer B. quadrilateral, if I’m understanding it right. I am terrible at explaining things and I can’t mark up the diagram, but a tetrahedron is a three dimensional shape and there are too many missing variables missing for me to play with to say if it’s C. or D. for sure (not like I’m an expert, just a fellow student trying to help). I don’t know if you’re on a time crunch but I hope this helps and fingers crossed someone qualified will answer this.