Statements:
No lessons are topics.
All topics are headings.
Some headings are introductions.
All introductions are conclusions.
Conclusions:
I. Some lessons are introductions.
II. Some conclusions are headings.
III. Some headings are not conclusions.
IV. Some lessons are not conclusions.
Some headings are introductions.(I) + All introductions are conclusions.= Some headings are conclusions (A) ⟹ conversion ⟹ Some conclusions are headings. Hence conclusion II will follow.