Answer:
Germanic invaders, Christianity and Islam 
 
        
             
        
        
        
B - the line was long, noisy, and miserable.
Coordinate adjectives are adjectives that appear in a sequence with one another and modify the same noun. An example is the soft, fluffy kitten.
 
        
             
        
        
        
Steve jobs believe that his decision to drop out from college and learn calligraphy is what makes an apple an all an all different technology from other. Right after he dropped out from REEDS, he had no idea what he wanted to do. To just learn something fresh, he decided to learn calligraphy.
        
             
        
        
        
It should not be controversial: it would only make the research less  reliable since people would have their opinions about the topic that they would want to defend.  It should also not be obscure: then it's hard to check. 
The best answer is that it should be multifaceted: it should include a number of aspects, not just one, so that the test can check for those aspects, not just one.