HELP PLEASE ITS MULTIPLE CHOICE Why is the total mass of the atoms before and after a reaction the same?

A) because The equation is unbalanced

B) Because your reaction can happen in both directions

C) some of the Atoms have become different kind of atoms.

D) all the atoms are still there, just connected in different ways

b, because your reaction can happen in both ways

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]