Question

Which of the following is not a diameter?

SV
RU 
WT

Answer 1

WT
It does not perfectly cut the circle in half.

Answer 2

The center of the circle is point A
 the diameter would be a line with 2 points that cross through point A
 
the line with points WT cross through pint  which is not at the center (Point A)
 so WT would not be a diameter.