Mechanical slicing

This is a sectional view, which cannot be drawn completely according to the sectional view and view;

1A and 2B: obvious errors. The holes and pits formed by the revolving surface shall be drawn according to the sectional view; Moreover, the cutting of more than two intersecting cutting planes should be broken in the middle, which is called single cutting and should not be broken.

3C: Error, the holes and pits formed by the rotating surface should be drawn according to the sectional view, therefore, intersection lines (intersection lines and intersection lines) should not be drawn here; In fact, if you draw according to the view, this intersection line is also wrong, and the intersection line on the left and right sides is not drawn;

4D, correct;