The expression for arc length in polar form is_________________

• A. \(ds = \int_a^b \sqrt{r^2 + (\frac{dr}{dθ})^2} \)
• B. \(ds = \int_a^b \sqrt{r^2 + (\frac{dr}{dθ})^2} \,dθ \)
• C. \(ds = \int_a^b \sqrt{(\frac{dr}{dθ})^2} \,dθ \)
• D. \(ds = \int_a^b \sqrt{r^2 + (\frac{dr}{dθ})^2} \,dr \)