In the given question, a sentence is divided into five parts out of which the last part is correct. Out of the remaining four, there are errors in three parts. Choose the part which doesn't have an error. If all the parts are correct, mark 5 i.e. All are correct as the answer.

One in the most (A) puzzle questions about depression (B) is why it's incidence (C) is higher among (D) girls than boys.