(a)78% nitrogen, 21% oxygen, 1% argon and other inert gases, such as carbon dioxide.(b)78% oxygen, 21% nitrogen, 1% phosphate and other inert gases, such as carbon dioxide.(c)78% carbon dioxide, 21% nitrogen, 1% oxygen and other inert gases.(d)78% phosphate, 21% nitrogen, 1% oxygen and other inert gases, such as carbon dioxide.