Which of the following statement(s) is/are TRUE?

I. $$\frac{1}{1 \times 3}+\frac{1}{3 \times 5}+\frac{1}{5 \times 7}+.......+\frac{1}{11 \times 13} = \frac{12}{13}$$

II. $$\frac{1}{1 \times 2}+\frac{1}{2 \times 3}+\frac{1}{3 \times 4}+.......+\frac{1}{12 \times 13} = \frac{12}{13}$$

$$\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+.......+\frac{1}{11\times13}$$

$$=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}+-\frac{1}{7}.......+\frac{1}{11}-\frac{1}{13}\right)$$

$$=\frac{1}{2}\left(1-\frac{1}{13}\right)$$

$$=\frac{6}{13}\ .$$

I is not correct .

And, 

$$\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+.......+\frac{1}{12\times13}$$

$$=\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}.......+\frac{1}{12}-\frac{1}{13}\right)$$

$$=\left(\frac{1}{1}-\frac{1}{13}\right)$$

$$=\frac{12}{13}\ .$$

So, II is correct .

B is correct choice.