<span> Light waves are a wave in the electromagnetic field, this field may exist in a vacuum. Sound needs either solid, liquid, or gas to propagate and therefore it is called a mechanical wave. Sound is a form of energy which is transferred by vibrating air molecules if motions of propagation is air.</span>
Crylo i think is the correct answer
Elements in same group / family tend to have similar properties ( but not exactly the same). Since, iron and silver are in two different group / families, they have different properties.
Also, Silver and iron have different properties because they have different atomic structure. Having different atomic structure means bonding differently with other elements. So, they have different properties.
To calculate atomic mass, you have to take to weighted average of the isotopes' masses. What that means is M = RA*106 + (1 – RA)*104, where RA is relative abundance expressed in decimal form. If you simplify the right side of that equation, you get M = 2*RA + 104. Doing a little more algebra yields RA = (M –104)/2 = (104.4 – 104)/2 = 0.4 / 2 = 0.2, which is 20%. So the answer is B.
