6. Ms. Carol promises: In the upcoming exam, students who answer all multiple-choice questions correctly will receive an excellent award. Which of the following statements is correct? ( ).
(A) If Louis did not receive the excellent award, then he got all multiple-choice questions wrong.
(B) If Louis did not receive the excellent award, then he got at least one multiple-choice question wrong.
(C) If Louis got at least one multiple-choice question wrong, then he did not receive the excellent award.
(D) If Louis received the excellent award, then he answered all multiple-choice questions correctly.
(E) If Louis received the excellent award, then he answered at least one multiple-choice question correctly.
6. B.

Original statement: If all multiple-choice questions are answered correctly, then an excellent award is obtained.

Contrapositive: If an excellent award is not obtained, then at least one multiple-choice question is answered incorrectly.

Since the original statement is equivalent to the contrapositive, option $\mathrm{B}$ is logically correct.