I)A mathematician can never add two numbers correctly, but can always add three numberscorrectly.
Here A got incorrect answer for 2 numbers ,So, A is mathemetician
B got incorrect result with 3 numbers - B is not a mathematician
C got correct result with 2 numbers - C is not a mathematician
Ans A) if the question can be answered by any one of the statements alone, but cannot be answered by using the other statement alone.