The author tells us that a story of our universe is in some respects similar to a typical Hollywood action movie, where everything happens just right to ensure that the hero survives. The laws of physics are so finely tuned as to support life, that the whole existence of such a universe seems improbable. Some cosmologists have tried to reconcile this paradox by hypothesizing that our universe is just one of many within a wider array called the multiverse. Given a sheer number of possibilities, nature would have had a good chance to get the right set of laws of physics in place to support life as we know it.
The author then questions the assumption that the laws of physics are so fine-tuned by arguing that it arises largely from the difficulty in identifying an alternative set of laws that would be compatible with life. The scientists tend to tweak one parameter at a time, but if one manipulates multiple constraints at once, it is possible to identify scenarios where physical laws are different from our own but can still support life.
The author then concludes that even even though finetuning has been used as indirect evidence for the multiverse, his findings are consistent with the idea of the multiverse because (a) certain models of the birth of the universe would lead us to expect the existence of the multiverse and (b) the multiverse concept may well prove to be the source of solutions to certain other long-standing puzzles in cosmology.
(B) is incorrect because while it accurately expresses one of the ideas in the passage, it is not the main point. In fact, it is only one of the two considerations for the author's argument that his findings are compatible with the idea of the multiverse, whereas (A) accurately describes the main point or the overall goal of the passage that is for the author to introduce evidence challenging the idea of the universe being so fine-tuned as to be the only set of physical laws supporting life.
