Answer:
2cm
Step-by-step explanation:
First, it is important to define both the radius and diameter. A diameter is the length of a line through the center of a circle that touches two points on the edge.
In the semicircle on the top, if we can imagine it making up a full circle, we can note that the bottom center of the semicircle is the center of the full circle, with the line of length 4cm going right through it. Similarly, for the bottom semicircle, as the line between the semicircles is straight, the diameter for that one is 4cm as well.
The radius is equal to half of the diameter. The diameter is 4cm, so the radius is 4cm/2 = 2cm
