Rank the following in order of increasing (lowest to highest) reactivity: a) Na, Rb, Li

b) S, P

c) Xe, Rn

d) W, Hg, Cs

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).

Any vitamins or supplements can be obtained without prescription and are widely used as alternative from western medications. most supplements are not valued by the fda or any other drug and food agencies.