The line tangent to the graph of $f(x) = 3 x$ at $(0,0)$

A. is $y = 0$.

B. is $y = 3$.

C. is $y = 3 x$.

D. does not exist.

E. is not unique because there are infinitely many tangent lines.

In the answer box below, explain your reasoning for the choice you made above. Use complete sentences and correct grammar, spelling, and punctuation. Be specific and detailed. Write as if you were explaining the answer to someone else in class.