The method of drawing a tangent to a circle with center O from an external point P is given below.
- Line segment OP is drawn.
- The midpoint M of line segment OP is determined.
- A circle with center M and diameter [OP] is drawn.
- The intersection points of the circles with centers O and M are marked. Let one of these points be T.
- Ray [PT is tangent to the circle with center O at point T.
In this construction, if the radii of the circles with centers O and M are 4 cm and 3 cm respectively, what is the length $| PT |$ in cm?
A) $3 \sqrt { 3 }$
B) $2 \sqrt { 5 }$
C) $\sqrt { 7 }$