mansianand1234
how do I identify here that 'stunning' is not ing verbal but part of absolute phrase
I thought ing verbal is incorrectly used here.
The only way to tell what the function of "stunning" is in this context is to consider the meaning conveyed.
We can see that it doesn't make sense to say that, when researchers unearthed 400,000-year-old wooden spears, the researchers were "stunning evidence." Thus, as you indicated, logic dictates that "stunning evidence ..." cannot be a participial phrase that modifies the preceding clause.
However, we don't stop there. Rather, we have to consider whether a different meaning makes sense.
Doing so, we see that "stunning evidence" can be an appositive that renames "400,000-year-old wooden spears from what appears to be an ancient lakeshore hunting ground." The spears and hunting ground represent "stunning evidence that human ancestors systematically hunted big game much earlier than believed."
In that case, "stunning" is a participle that modifies "evidence."
Since the sentence is properly constructed and the meaning conveyed makes sense, the (D) version is correct.