The diagram that shows how to set a pair of compass to draw a circle with diameter 5cm is figure B
The diameter of a circle is the distance across its center, passing through the circumference. It is twice the length of the radius.
Mathematically,
d = 2r where r is the radius of the circle and d is the diameter of the circle.
since the diameter is 5
r = 5/2 = 2.5cm
To use a compass to draw a circle, we measure the compass with radius not the diameter.
Therefore, the diagram that shows how to set a pair of compass to draw a circle with diameter 5cm is figure B.