题目

阅读理解 Lying alongside mountains of smelly garbage under the South American sun, Cateura is a long way from the conservatories of Prague or Vienna. Yet the township, which grew out of Paraguay's largest dump(垃圾场), is gaining a reputation as a hothouse for musical talent and for its youth orchestra(管弦乐队) that plays instruments made from garbage. The world sends us garbage. We send back music, says Favio Chavez, leader of the Recycled Orchestra, during a recent visit by the group to Los Angeles. Orchestra members, poor children from Cateura, play violins fashioned from oven t如图，在直三棱柱ABC﹣A1B1C1中，点M、N分别为线段A1B、AC1的中点． （1）求证：MN∥平面BB1C1C；（2）若D在边BC上，AD⊥DC1 ， 求证：MN⊥AD．