The correct answer is (B).
(B) Weaken
Step 1: Identify the Question Type
The question directly asks for something that will weaken the argument.
Step 2: Untangle the Stimulus
The archaeologist concludes that Neanderthals probably preserved meat by smoking it. The evidence is the presence of burnt lichen and grass, which produce a lot of smoke but not as much heat or light as wood.
Step 3: Make a Prediction
The archaeologist is making two assumptions. First, the archaeologist assumes that the smoke created by the lichen and grass was used for smoking meat, and for no other reason. Second, the archaeologist assumes that the light and heat produced by lichen and grass was not good enough for Neanderthals, i.e., they would have used wood (or something similar) if they really wanted light and heat. The correct answer will contradict one, if not both, of these assumptions by suggesting that the lichen and grass was used for another reason or that it provided enough heat and light.
Step 4: Evaluate the Answer Choices
(B) is correct. Wood might make for a warmer, brighter fire if it's available, but if it wasn't, and nothing in the area was better than lichen and grass, then it's possible the lichen and grass were used for heat and light and not for smoking meats.
(A) is a 180. If there were other fireplaces that were used to produce more heat, then the fireplaces with the lichen and grass were probably used to produce smoke, which would only strengthen the archaeologist's view.
(C) is a 180, indicating that Neanderthals went to great lengths to procure lichens. This suggests it was important to have a smoke-producing substance, thus strengthening the archaeologist's view.
(D) is Out of Scope. The archaeologist is not claiming that all Neanderthals preserved all of their meat by smoking it. Even if there were some later Neanderthals that developed an alternative method for some of their meat, the archaeologist's argument still stands.
(E) is a 180. This offers a reason why smoking meat would be beneficial, thus adding support to the archaeologist's claim.