**Correct option (C) 10**

**Explanation: **

At point A, the path diference is 2.5 and at B, path difference is zero. While moving from A to B, path difference changes from 2.5 to zero, making two maxima corresponding to 2 and (excluding B). B is common for both upper quarter circles hence there are five maxima in one half circle, making 10 in total circular movement.