Of the following series of partial sums which might arise in the addition of 36 and 25, the one that is incorrect is: a) 11, 31, 61 b) 11, 4, 6, 61 c) 11, 41, 61 d) 36, 56, 61

Note that
25 + 36 = 61.

The partial sums of 61 are
1, 3, 6, 10, 15, 21, 28, 36, 45, 55.

These numbers arise in partial sums of 61.
4 = 1 + 3
6 is a partial sum
11 = 1 +10
31 = 10 + 21
36 is a partial sum
41 cannot be obtained from partial sums.
56 = 28 + 28
61 is a partial sum

Test the given answers.
A) 11,31,61 qualify as partial sums. It is correct.
B) 11,31,61 qualify as partial sums. It is correct.
C) 11 and 61 qualify as partial sums, but 41 does not. It is incorrect.
D) 36,56,61 qualify as partial sums. It is correct.

C) is incorrect.