Square pyramid is the pyramid with square base
Now to answer this question , we have to check which figure has a square base
First one - no , it does now has a square base
Second - again no , it also does not has a square base
Third - YES , it has a square base , and also the reast 4 sides are triangle with same sides
lets check fourth also
Fourth - No it does not have a square base
So Answer is third one
Third Option is the net of a square pyramid