Read the following excerpt. For a country said to be uninterested in its past, this would seem to be a giant exception to the rule. There are few if any
decisive new facts remaining to be unearthed. There continue to be bands of Lincoln assassination enthusiasts who find it
irresistible to speculate about what did or did not happen those fateful days in the spring of 1865. But they don't explain th
passionate interest in the man.
What inference can you make based on the underlined portion of the text?
Lincoln assassination enthusiasts have contributed meaningfully to research on his death.
During the spring of 1865, experts unearthed new facts about Lincoln.
The circumstances surrounding Lincoln's death remain somewhat unclear.
O Bands of Lincoln assassination enthusiasts speculate about why Americans aren't interested in their past.

The circumstances surrounding Lincoln's death remain somewhat unclear.

Explanation:

We can use the process of elimination to find the truest inference out of the inferences given to us.

"Lincoln assassination enthusiasts have contributed meaningfully to research on his death."

The passage provided contains nothing about the assassination enthusiasts possessing research on his death. It only says, "There continue to be bands of Lincoln assassination enthusiasts who find it iresistible to speculate about what did or did not happen those fateful days in the spring of 1863."

"During the spring of 1865, experts unearthed new facts about Lincoln."

The passage states, "There are few if any  decisive new facts remaining to be unearthed." This means that experts are still trying to find solid facts about him, let alone facts about Lincoln himself. Experts are clueless about Lincoln, so unearthing any bit of information about him is most likely rare. And even if they did find any information on him, they wouldn't be certain if it wouldn't be solid.

"Bands of Lincoln assassination enthusiasts speculate about why Americans aren't interested in their past."

In the passage, it solely includes, "For a country said to be uninterested in its past, this would seem to be a giant exception to the rule." It does not inform us that the "Bands of Lincoln assassination enthusiasts" directly does this, nor does it imply anything about Americans.

Therefore, inference is the third option.

I hope this helps you in any shape or form.