When historians talk about the present they are referring to events thata are unlikely to ever occurb have not yet occurdc will happen years from nowd are happening at this time

The present is a time frame that is usually happening at the moment. it could be D. 

For me the answer would be D. Yes, i know D is true especially in English. But we are referring to History. You when it comes to History!  History are like hmm think of films of a movie. Like maybe in a Museum! Like agent stuff you know. They explore the PRESENT. Sometimes they explore about something that happened years and years ago , which is the PAST. 

I really hope this helps and answers your question! 

I Wish You The Best Of Luck! :)

The answer would be option a , b, and c.