“旧时王谢堂前燕，飞入寻常百姓家。”常被用来形容过去的一些昂贵商品现在变成大众消费品，造成这种变化的主要原因是（ ）。

(单选题)黄河流域半坡类型彩陶纹饰出现最多的是（ ）。 (单选题)What is the writer trying to do in this passage? (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 ______.