joealam1 wrote:In 1974 a large area of the surface of Mercury was photographed from varying distances, which revealed a degree of cratering similar to that of the Moon's.

A.which revealed a degree of cratering similar to that of the Moon's
B.to reveal a degree of cratering similar to the Moon
C.revealing a degree of cratering similar to that of the Moon
D.and revealed cratering similar in degree to the Moon
E.that revealed cratering similar in degree to that of the Moon

OA:C
[spoiler]
E was the runner up for me, i would like to discuss more about why E is wrong, honestly i just ruled it out because it sounded awkward to me.
Now that i am looking back i think i found two issues with it: 1) the comma preceding the "That" makes the sentence a fragment 2)"similar in degree" is not concise[/spoiler][/spoiler]

Another issue: consider the usage of "that." In this case, it seems to be used as a restrictive relative pronoun. To illustrate the difference between restrictive and non-restrictive pronouns consider the following:

1) The plot twist that revealed the killer was a delightful surprise. In this case, "that" is used as a restrictive relative pronoun modifying "the plot twist." It's restrictive in the sense that the phrase "that revealed the killer" is essential to differentiate this plot twist from other plot twists in the book. (Notice that there's no comma preceding "that.")

2) The plot twist, which revealed the killer, was a delightful surprise. In this case, "which" is a nonrestrictive relative pronoun, again modifying "the plot twist." In this case, "which revealed the killer" is nonrestrictive - the implication is that there is only one plot twist in the book so we don't need the phrase "which revealed the killer" to tell us which one we're writing about. Rather, it's additional information that might be interesting. (Notice that there is a comma preceding "which.")

The important element for the GMAT: when "that" is used as a restrictive modifier, and serves as the subject of a relative clause, it won't follow a comma.
When "which" is used as a nonrestrictive modifier, and serves as the subject of a relative clause, it will follow a comma.

Here "that" incorrectly follows a comma.