Fill in the Blank with One of the Words or Phrases

Multiple Choice

Fill in the blank with one of the words or phrases listed below.

-Theــــــــــــــــــــــــــــ formula is $\left( \frac { x _ { 1 } + x _ { 2 } } { 2 } , \frac { y _ { 1 } + y _ { 2 } } { 2 } \right)$ .

A) distance
B) midpoint
C) index
D) conjugate