Points G and F are both on the bottom face, so the third missing point must be also on the bottom face. The third point is either H or E. Since H isn't listed in the answer choices, it has to be point E. The only answer choice that has point E is the third choice EFG
Answer: Triangle EFG
See the attached image to see the triangle EFG. The right angle (aka 90 degree angle) is at point E. The hypotenuse GF is opposite the right angle. The hypotenuse is ALWAYS opposite the right angle. This is because the longest side is always opposite the largest angle of the right triangle. The 90 degree angle is the largest angle of the right triangle.
