3D打印参照的是打印技术原理，能够将计算机设计出的物体直接打印出实物。该技术将对航空航天、汽车、医疗等核心产业的革新有巨大推动作用。但3D打印是材质一层层堆积形成的，每一层都有厚度，这决定了它的精度难以企及传统的剪裁制造方法。这说明（ ）
①创新推动生产力和思维的进步 ②矛盾的主要方面和次要方面是辩证统一的
③主要矛盾和次要矛盾是辩证统一的 ④新事物是在否定旧事物的基础上发展的
A：①②
B：①③
C：②④
D：③④
目前人们认为很理想的一种生物反应器是
Tang Hai is chatting with his e-pal David on QQ (T: Tang Hai D: David)D: Hi. How is it going these days?T: Pretty good! We celebrated our Dragon Boat Festival(端午节) last week.D: Dragon Boat Festival?1T: To remember an ancient Chinese poet(诗人)。D: How do you usually celebrate it? T:2 But this year, we did something more interesting.D: What did you do?T: Our school had a Dragon Boat race.D:3 who won the race?T: Our class.D:4T: Thanks a lot. I hope you can come to China sometime.D:5 I'm interested in Chinese traditions. Tell me more about them next time.T: Ok, I will. See you.D: See you!
我国水资源空间分布不均，解决此缺陷的方法是（ ）
