The logic follows here is :-
The least possible Venn diagram for the given statements is as follows,
Conclusion:I. No brave are boys → False (No direct relation given hence, false).
II. All brave are cruel → False (It can be possible not definite hence, false).
III. Some brave are not cruel → False (It can be possible not definite hence, false).
Conclusion II and III forms a complementary pair for either or.
Thus, the correct answer is 'Either conclusion II and III follows'.