良性肿瘤与恶性肿瘤的根本区别是（）
A.肿块硬度
B.细胞分化程度
C.生长速度
D.表面光滑程度
E.疼痛程度
参考答案：B
His wife was ill in hospital, but____ it didn't havemuch influence on his research work. [ ]
A. fortunately
B .eventually
C. certainly
D. surprisingly
实际生产中，分体制造的大型砂芯可用易熔合金将其各部分连接在一起。
