we know that
10*pi/3------> convert to degrees------> 10*180/3=600 degrees
600=360+240
240 degrees belong to the III quadrant
so
the x-coordinate is negative
the y-coordinate is negative
240°=180°+60°
60 degrees is the angle to find the terminal point
let
∅=60°
in the unit circle
r=1 units
x=-r*cos ∅----> x=-cos 60------> x=-(1/2)
y=-r*sin ∅----> y=-sin 60------> y=-(√3)/2
the point is
therefore
the answer is the option D