$\left(\mathrm{I} / \mathrm{Fe}\right)$ is the chemical symbol of Iron.

$\mathrm{A}$: ${\mathrm{H}}_2{\mathrm{SO}}_4$

$\mathrm{B}$: ${\mathrm{HNO}}_3$

$\mathrm{C}$: ${\mathrm{H}}_2{\mathrm{SO}}_3$

Enter your correct answer as $\mathrm{A}, \mathrm{B},$ or $\mathrm{C}$.

Match the following: 

Two or more substances simply mixed together, but not chemically combined, is called a/ an _____.

Reddish-brown deposits on the surface of iron objects is called: