Answer:
The quality that the essay should have to meet the requirements for the assignment is:
B. It should include only provable information.
Step-by-step explanation:
The adjective "expository" refers to something whose intention is to explain an idea, topic, or fact. An expository essay will, thus, focus on explaining an idea and, to do so, it will rely on investigation and evidence. The evidence and the information that will support the explanation must be provable. In other words, they must be solidly true.
As we can see, an expository essay will not aim at persuading the audience or focusing on the author's opinion, much less on creating a historical fiction.