Select the correct option to test your answer: A $$\frac{{\text{r}}}{4}$$ B $$\frac{{\text{r}}}{8}$$ C $$0.134{\text{ r}}$$ D $$\frac{{3{\text{r}}}}{8}$$ Correct Answer: Option D ($$\frac{{3{\text{r}}}}{8}$$) Verified correct option for Civil Engineering (Strength Of Materials).