Name the intersection of the three planes shown.

Ignore the circle and arrow.

Your question isnt clear. but endosymbiosis means earlier bigger prokaryotes engulfed prokaryotes that carried out aerobic respiration(later became mitochondria) and other prokaryotes that carried out photosynthesis(later became chloroplasts). these “now” mitochondria and chloroplasts “realised” that they couldnt survive without the bigger prokaryotes that engulfed them hence they remained part of the larger prokaryotes. hope that explains it.