烟酸缺乏引起的“三D”症状包括（）、（）和（）。
参考答案：皮炎；腹泻；痴呆
Part 31. What are the effects of parks on people’’s life2. How many Chinese have their own gardens3. If you have a garden in the future, what plant will you like to grow, and why
为安全使用，喷砂和空气软管接头应用金属丝连接在一起
