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.

-Theـــــــــــــــــــــــ formula is $\mathrm { d } = \sqrt { \left( \mathrm { x } _ { 2 } - \mathrm { x } _ { 1 } \right) ^ { 2 } + \left( \mathrm { y } _ { 2 } - \mathrm { y } _ { 1 } \right) ^ { 2 } }$ .

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