Mark the letter A, B, C, or D to indicate the correct answer:John __ this task yesterday5/30Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions. John ______ this task yesterday morning, but I did it for him. He owes me a thank-you.must have completedmay have completedshould have completedcould have completedGiải thíchĐáp án C.