$\begin{array}{1 1} (a)\; \text{78% nitrogen, 21% oxygen, 1% argon and other inert gases, such as carbon dioxide.} \\ (b)\; \text{78% oxygen, 21% nitrogen, 1% phosphate and other inert gases, such as carbon dioxide.} \\ (c)\; \text{78% carbon dioxide, 21% nitrogen, 1% oxygen and other inert gases.} \\ (d)\; \text{78% phosphate, 21% nitrogen, 1% oxygen and other inert gases, such as carbon dioxide.} \end{array}$
