​Horizontal to V4 at midaxillary line

A) ​V₁
B) ​V₂
C) ​V₃
D) ​V₄
E) ​V₅
F) ​V₆

Horizontal

Not vertical; flat and even; level; parallel to the plane of the horizon.

Midaxillary Line

An imaginary line running vertically down the surface of the body passing through the apex of the axilla (armpit).