Pankaj0901
In Option A-
A) to make ever more precise measurements that scientists hope will enable them to
"that" refers to "measurements"? Or, "that" is initiating a substantive clause: "that scientists hope will enable...."? How do we know which one it is? I rejected A thinking that "that" is wrongly modifying "measurements".
In (A), "that" introduces a phrase that correctly modifies the noun "measurements."
A simplified example would be something like this: "Halfway through the voyage, I began to miss the items
that I had rashly thrown overboard in a fit of rage." Everything starting with the word "that" just adds more information about the noun "items."
Similarly, everything after "that" in the official question just gives us more information about the "measurements." Specifically, these particular measurements are ones that "scientists hope will enable them to understand how the solar system formed some four billion years ago."
I wouldn't worry about any of the jargon about types of clauses. We could get into a very geeky discussion about the nuances of, say, substantive clauses and relative clauses, but it probably wouldn't do anything to help your GMAT score. As long as you understand the function of the phrase beginning with "that", you're in good shape.
For more information about the word "that," check out
this article.
I hope that helps!