Father has been working all day. He must be tired now.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

Father has been working all day. He must be tired now.

• A. I'm sure that Father is tired after working all day.
• B. Father must work all day and tired now.
• C. I think Father was tired all day working.
• D. Father thinks he is tired now because he has been working all day.