_____ he lives alone, he doesn't feel lonely. [ ]
A. If
B. Because
C. When
D. Although
答案:D
伤寒的病理特点是全身单核-巨噬细胞系统的增生性反应
成型铣刀为了保证刃磨后齿形不变,一般都采用()。
A.铲齿铣刀
B.折齿铣刀
C.尖齿铣刀
D.直齿铣刀