1. **State the problem:** Reduce the fraction $\frac{231}{1001}$ to its lowest terms. 2. **Formula and rules:** To reduce a fraction, divide numerator and denominator by their greatest common divisor (GCD). 3. **Find the GCD of 231 and 1001:** - Prime factorize 231: $231 = 3 \times 7 \times 11$ - Prime factorize 1001: $1001 = 7 \times 11 \times 13$ - Common factors: $7$ and $11$ - GCD = $7 \times 11 = 77$ 4. **Divide numerator and denominator by GCD:** $$\frac{231}{1001} = \frac{\cancel{77} \times 3}{\cancel{77} \times 13} = \frac{3}{13}$$ 5. **Final answer:** The fraction reduced to lowest terms is $\frac{3}{13}$. This corresponds to option (c).