Answer

a

Explanation

To solve this type of complicated problem, make as many dots in the main design as there are samll designs .
In the problem figure (a) to (b), we see that there is movement of left upper design by 1/2 arm in clockwise direction to become central middle design , central design by 1/2 arm in clockwise direction to become right lower design and so on.
Similarly , in the problem figure (b) to (c) left upper design move by 1/2 arm in anti-clockwise to become central designs do not changes it position in upper corner and lower corner , respectively Now, we should move from problem figure (a) to problem figure (b) and so on to detect the pattern.