This could strengthen the argument by showing that Neanderthals burned other material for heat, which suggests lichen and grass were not being burned for heat.

This raises the possibility that Neanderthals burned lichen/grass for heat/light. Although wood can produce more heat/light, (B) tells us the Neanderthals didn’t have access to it. So, they might have used lichen/grass for heat/light because it was the best available material.

This suggests lichen was brought long distances. This is consistent with the theory that it was burned for its smoke.

This concerns other groups living more recently that developed other methods of preserving meat. But the argument is about what conclusions we can draw about the Neanderthals who used the fireplaces around which burnt lichen and grass have been found.

If anything, this strengthens the argument by suggesting Neanderthals had a strong reason to preserve meat by smoking.