Statement 1: If one letter is placed in an incorrect envelope, then the letter that belongs to that envelope must also be placed in an incorrect envelope. Therefore, it’s not possible for only one letter to be misplaced; either no letter will be misplaced, or at least two letters will be misplaced. Thus, Statement 1 is incorrect.

Statement 2: To fulfill the requirement of placing two letters in correct envelopes and two in incorrect envelopes, we can choose the two letters to be placed in correct envelopes in 4C2 ways, which equals 6 ways. The remaining two letters will automatically be placed in each other’s envelopes (i.e., incorrect envelopes). Therefore, Statement 2 is correct. Hence, option (b) is the correct answer.