$$\left\{\frac{1}{3}, \frac{1}{5}, \frac{1}{7}, \frac{1}{9}\right\}, \left\{\frac{1}{12}, \frac{1}{15}, \frac{1}{18}, \frac{1}{21}\right\}, \left\{\frac{1}{25}, \frac{1}{29}, \frac{1}{33}, \frac{1}{37}\right\}, \left\{\frac{1}{42}, \frac{1}{47}, --------, \frac{1}{57}\right\}$$

A

$$\frac{1}{50}$$

B

$$\frac{1}{51}$$

C

$$\frac{1}{52}$$

D

$$\frac{1}{53}$$