Need help! Why is the answer D

@Cynthia-lee we know from the passage that the marks resemble worm tracks. However, since they were made well before worms existed on Earth, the marks must have been made from something else. The argument claims the marks were likely made by geological processes. (D) weakens that argument because it says marks resembling worm tracks could not have been made by geological processes in that place, at that time. I hope that helps!

Why is C incorrect?

@Shiyi-Zhang, Happy to help. (C) says, "There were some early life forms other than worms that are known to have left marks that are hard to distinguish from those found in the piece of sandstone." With (C), we know that there existed other life forms that were worm-like and left similar marks to works in prehistoric times. However, this information doesn't provide us with support to weaken the argument because these organisms would also exist far after the mark was made on the sandstone since they're multicellular. (C) doesn't expand the earliest date that a multicellular organism was known to exist, so it doesn't weaken it. The facts in the argument that the marks were dated 500 million years before any multicellular life still stand. Does this make sense? Let us know if you have any other questions!

I'm unclear why the other organisms would have had to be multi-cellular? What if they were a single-called organism that could have left the tracks? And with regards to D- it says the place where the sandstone was found. What if the sandstone had been moved?

My thoughts were aligned exactly with David as to why C makes more sense than D. Could we please get further explanation?