The correct answer is C. Let us solve for the answer step by step. Assuming that all mammals in the problem have a complete number of legs we can start solving it. A dog has four legs, and the problem states four dogs, so 4x4=16. An elephant has four legs multiplied by two is 8, a cat has four legs multiplied by 15 is 60.
For the four-legged mammals, the total number of legs is 84 (16+8+60). Lastly, a human has a pair of legs, so 2x26 is 52. Add 84 and 52 together, and you will get the final answer of 136. Solving this kind of problem is more comfortable to write on paper or a notepad so you will not be confused about solving it mentally.