they find people who rejected violence on principle and others (like john brown) who saw violence as the only way to stop much...
i am not too sure there is a clear answer to this question: in principle, you could hold a speech of 10 minutes on any topic, but the depth of the treatment of the topic would have to be adjusted.
i would choose answer c. the history of modern interior design: describing a history of anything requires a lot of details, and those need time.
specifically, i find that options a and b are very easily condensed for 10 minutes: they are in any case not good options.
d. depends on whether this is just a general introduction or a very detailed, practically oriented, tutorial.