In 1995 Richard Stallman, a well-known critic of the patent system, te

The biggest thing that jumps out at me here is the word "and." Something has to be parallel with the phrase that follows the word "and." And I think we're in good shape: "... one of Kirchhoff's laws, an observation about electric current first made in 1845 and now included in virtually every textbook of elementary physics." Cool, "first made in 1845" and "now included in virtually every textbook" both modify "an observation about electric current" -- and that makes perfect sense.

So let's keep (A).


The "which" jumps out at me first in (B): "which was an observation..." modifies "one of Kirchoff's laws." That's OK, though we probably don't really even need the phrase "which was." It's not a big deal, but (A) is more succinct because it skips those extra couple of words. That's not a definite error, but it's a mild reason to prefer (A) over (B).

The bigger problem is the parallelism. Following the "and", we have a brand-new clause: "it is now included in virtually every textbook..." But I don't think that the clause is logically parallel to anything. And more importantly: there's no good reason to start a brand-new clause here, partly because we're just trying to describe the observation, so a simple modifier would be cleaner than a brand-new clause.

So (B) isn't a complete disaster, but it's definitely not as good as (A).


This is a classic comma splice:

• Independent clause #1: "In 1995 Richard Stallman, a well-known critic of the patent system, testified in Patent Office hearings that, to test the system, a colleague of his had managed to win a patent for one of Kirchhoff's laws..."
• Independent clause #2: "...it was an observation about electric current first made in 1845 and now included in virtually every textbook of elementary physics."

Those two independent clauses are separated by only a comma, and that's not cool. (Commas and comma splices are very briefly discussed in this YouTube video on GMAT punctuation if you're curious to learn more about that crap.) So we can eliminate (C).


(D) has basically the same comma splice problem as (C):

• Independent clause #1: "In 1995 Richard Stallman, a well-known critic of the patent system, testified in Patent Office hearings that, to test the system, a colleague of his had managed to win a patent for one of Kirchhoff's laws..."
• Independent clause #2: "...it is now included in virtually every textbook of elementary physics."

So (D) is out, too.


(E) isn't a total disaster, but it's definitely not as good as (A).

For starters, I'm not sure why we would say something like "...one of Kirchoff's laws that was an observation about electric current..." First, there's no good reason to emphasize the past tense in this case: sure, the observation was first made in the past, but there's no good reason to suggest that the law itself somehow existed only in the past -- and that's exactly what seems to be happening in (A). Second, the phrase "one of Kirchoff's laws that was an observation about electric current" suggests that Kirchoff had other laws that were NOT about electric current, and we have no idea if that's actually the case.

The other problem is the placement of the modifier "first made in 1845." This is subtle and annoying, but because "first made in 1845" is surrounded by commas (an appositive phrase, if you like grammar jargon), it seems to modify ONLY the preceding noun, "electric current." So if we think about the sentence strictly and literally, it's saying that electric current was first made in 1845, and that's really not what the sentence is trying to say -- it's trying to say that the observation was first made in 1845, not the electric current itself.

So (E) can be eliminated, and (A) is the best we can do.