Three statements (S1, S2, S3) regarding circulation are given. Identify the incorrect statement:
S1: The concept of circulation is important for the theory of drag.
S2: Circulation around a contour is equal to the multiplication of vorticities within the area of the contour.
S3: Circulation around a contour follows Stokes theorem.
1
S1 only
2
S2 only
3
S1 and S2
4
All are incorrect.