ans A .Divide the circle into two halves vertically.on the right half add 2 to 3 and get 5 which is on the other half{bottom}.NEXT add 3 to 4 to get 7 which is on the other half.Again add 4 to 5 to get 9 which is on the left half.So therefore 5 + 5 is 10. now you'll go to the left half and 7-5 is 2 which is on the right half.