AIDS would be the disease you're referring to:)<span />
The two main reasons why Douglass opposed John Brown in his plan to raid Harpers ferry is because first he was sure that the plan would fail and thus it would lead to many black deaths. The second reason is that Douglas thought that this plan would hurt the abolition movement due to a backlash.
C. The Iran Hostage Crisis
The study of earth, like map reading, locations on the map, countries, continents, seas/oceans/lakes, mountains/hills (best way I could explain it, sorry if it doesnt make sense)