given a set of integers, does any non-empty subset of them add up to zero? That is a decision problem and happens to be NP-complete?

a net is a diagram that shows a “flattened” view of a solid. in a net, each face and base is shown with all of its dimensions. a net can also serve as a pattern to build a three-dimensional solid.

a pyramid is a three-dimensional object with a base that is a polygon and triangular faces that meet at one vertex.

" the net of a triangular pyramid consists of four triangles. the base here we are given of the pyramid is a equilateral   triangle, and the lateral faces are also triangles "

the answer is c: divide the arc's degree measure by 360°, then multiply by the circumference of the circle.