题目

阅读下面短文，从短文后所给各题的四个选项（A、B、C和D）中，选出可以填入空白处的最佳选项。 My 4-year-old son now enjoys posting letters. He has formed the 1of drawing pictures, writing his name on them, and then 2 the artwork in an envelope. He then insists on 3his handwork to the neighbors, and a mail box he 4 belongs to the elderly couple who live next door. To be 5, I didn't think much of it, but I had 6 to warn my neighbors of the drawings7 appearing in their letterboxes—I just didn't have the 8 to do so, because I was a little busy recently. On TuA、B、C、D为人类的四种疾病，下表是有关专家进行调查的结果，你认为其中属于遗传病的是（ ）遗传病非近亲婚配后代的患病率近亲婚配后代的患病率ABCDA．AB．BC．CD．D