I think the answer is either 40° or 60°??

60°

Step-by-step explanation:

According to Angle Sum Property of a triangle , sum of the angles of 3 sides of the triangle is always 180°.

Here the angles given are 80° & 40°. Let the 3rd angle be x. So using the Angle Sum Property here ,

40° + 80° + x° = 180°

=> 120° + x° = 180°

=> x = 180° - 120° = 60°

square pyramid

step-by-step explanation:

square prism looks like nothing like that

triangular prism has a rectangular base instead of a square base

tetrahedron has a triangular base