Tatsouka 2009

What is the value of $7$ $\dfrac{5}{7}$ $-$ $2$ $\dfrac{5}{6}$?
A. $4\dfrac{37}{42}$
B. $\dfrac{10}{13}$
C. $\dfrac{14}{13}$
D. $1$
E. $\dfrac{107}{42}$