# The sum of the series $\frac{1}{1.2} - \frac{1}{2.3} + \frac{1}{3.4} - ...$ upto $\infty$ is equal to :
( A ) $\log_e 2$
( B ) $\log_e 2-1$
( C ) $\log_e (\frac{4}{e})$
( D ) $2 \log_e 2$