81.（ ）

(单选题)The meaning of the underlined word “mature” in the passage i (单选题)Dennis’s example shows that successful people should _______ (单选题)From the story we know that the butterfly can’t fly because (单选题)Which sentence should go in the empty box in the last paragr (单选题)The first “it” in Paragraph 3 refers to（指的是）______. (单选题)What does the article mainly talk about？ (单选题)Sweet potatoes are good to people because they are rich in _ (单选题)From the passage we know that ______. (单选题)What can we know about sweet potatoes from the passage? (单选题)40.（ ）