"when a person steps on a tack with their left foot, flexor muscles on the right leg and extensor muscles on the left leg will be stimulated to contract."

You are working in the lab and are working with the same element but with varying isotopes of the element. you are working with c-11, c-13, c-14, and c-15. what is the average atomic mass of this element? (use periodic table) a- 12 b-15 c-14 d-13