question_answer

If \[f(r)=\pi {{r}^{2}}\], then \[\underset{h\to 0}{\mathop{\lim }}\,\frac{f(r+h)-f(r)}{h}=\]

A)                 \[\pi {{r}^{2}}\]

B)                 \[2\pi r\]

C)                 \[2\pi \]

D)                 \[2\pi {{r}^{2}}\]