锯割软厚工件应选用()锯条。

(A)粗(稀)齿;
(B)中齿;
(C)细(密)齿;
(D)任意一种齿距

(A)平锉;
(B)圆锉;
(C)半圆锉;
(D)三角锉

(A)方形孔;
(B)内角;
(C)平面;
(D)凹弧面