Correct Answer - Option 4 : Karan
Three Students: Tiara, Karan, and Chahal.
1. Only one of them told the truth in both statements.
2. Each of the other two gave one true and one false statement.
⇒ Both Tiara and Chalal in their Statement B have said that Karan has bought the notes.
⇒ Karan himself in his Statement B has accepted that he has bought the notes.
Therefore, it is clear that it was Karan who had bought the notes.
Hence, the correct answer is "Karan".