yea this is a tricky question. B is incorrect because...
1) The stimulus says there were MANY extinctions that didn't follow any known meteor impact; And that there are MANY records of major meteor impacts that do not seem to have been followed by mass extinctions.
2) Answer choice B says Major meteor impacts and mass extinctions cannot be consistently causally linked unless many mass extinctions have followed major meteor impacts.
B is consistent with what the stimulus says because there could be MANY meteor impacts that did result in mass extinctions, while at the same time MANY meteor impacts did not result in mass extinctions.
choice A uses the word ALL instead of MANY. With justify questions I always look for strong language over weak language.