C类配件指常用易耗配件，维修用量大、换件率高，库存周转快的曲轴、活塞及环、缸体、水箱、万向节等
参考答案：错
解析：A类配件指常用易耗配件
Joe, my close friend, moved to Beijing 10 years ago, and I ________ him since then. [ ]
A. don't see
B. didn't see
C. haven't seen
D. won't see
急性阑尾炎的主要病因是()。
A．细菌侵入
B．急性肠炎
C．肠道蛔虫
D．急性腹膜炎
E．阑尾管腔梗阻
