Add Do Not Use a Number Line Except as a Check

Multiple Choice

Add. Do not use a number line except as a check.
- $- \frac { 1 } { 7 } + \frac { 3 } { 7 }$

A) $- \frac { 2 } { 7 }$
B) $\frac { 2 } { 7 }$
C) $\frac { 4 } { 7 }$
D) $- \frac { 4 } { 7 }$