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experts, pls confirm my following idea.

Most of correct answer choices on strengthen/weaken question are based on assumption. The correct answer choice will confirm or cast doubt on an assumption. But for a few strengthening question, the correct answer choice is NOT based on any assumption but dirrectly support the conclusion. That correct answer choice is "general rule" said inhere.

Is my thinking correct? pls comment , experts.

The following question from gmatprep showing my idea.

Archaeologists in Michigan have excavated a Native American camp near Dumaw Creek. Radiocarbon dating of animal bones found at the site indicates that the camp dates from some time between 1605 and 1755. However, the camp probably dates to no later than 1630, since no European trade goods were found at the site, and European traders were active in the region from the 1620's onward.

Which of the following, if true, most strengthens the argument?

(A) Due to trade among Native Americans, some European trade goods would have reached the area before the European traders themselves did.
(B) At all camps in the region that have been reliably dated to the late 1620's, remains of European trade goods have been found.
(C) The first European trade goods to reach the area would have been considered especially valuable and preserved as much as possible from loss or destruction.
(D) The first European traders in the area followed soon after the first European explorers.
(E) The site is that of a temporary camp that would have been used seasonally for a few years and then abandoned.

oa is b. clearly, B is not based on any assumption.

why I put this point?. I will the reason after experts comment.