Magnetic Pole

[praachiee]

According to a recent study, Earth's magnetic north pole is moving away from Alaska and toward Siberia so rapidly, within 50 years, that the swirling green auroras of the Northern Lights might be visible in cities as far south as Rome, which is located at 41º north latitude.

rapidly, within 50 years, that the swirling green auroras of the Northern Lights might be visible in cities as far south as Rome, which is

rapidly, within 50 years, people may be able to see the swirling green auroras of the Northern Lights in cities as far south as Rome and

rapidly that, within 50 years, the swirling green auroras of the Northern Lights may be visible from cities as far south as Rome,

rapidly such that, within 50 years, people might be able to see the swirling green auroras of the Northern Lights from cities as far south as Rome, and

rapidly that, within 50 years, the swirling green auroras of the Northern Lights might be visible by people in cities far to the south; such as Rome,

The OA is C.
The explanation given is totally related to meaning:
"This sentence reports the striking findings of a research study: Earth's magnetic north pole is moving so fast that the Northern Lights may be visible from new locations within 50 years. The modifier within 50 years describes something that will happen in the future, so it cannot be referring to the fact that the north pole is (now) moving in a certain way. Rather, it must describe the study's conclusion that the Northern Lights will be visible from other locations in future.
(C) CORRECT. In this sentence, within 50 years is properly used to describe what will happen in the future. As far south as Rome is idiomatically correct, and the final modifier correctly describes Rome."

However, the logic I applied was : I eliminated A,B,D because they do not contain a 'that' to go with 'so rapidly'. The construction should be 'so rapidly that'. I did not really look at the rest of the sentence in these options, and so didn't consider the meaning factor.
Please let me know whether the construction 'so rapidly, within 50 years..' can be correct, and whether my approach to eliminate A and B was incorrect.

[jlucero]

Your logic is correct, but the reason why is the change in meaning that the explanation makes. A & D still have a "that" in the sentence, but the placement of the modifier "within 50 years" needs to be attached to the clause AFTER the that, rather than the part before. Note how the sentence changes meaning when the modifier goes on either side of this sentence:

The moon is moving so slowly that you won't be able to see it today.

vs

The moon is moving so slowly today that you won't be able to see it.

Is the moon moving slowly all the time? Or just today? We have a very similar example here. Is the north pole moving away within 50 years? Or does that main action happen all the time and the affect will happen within 50 years? The latter makes much more sense.

[wkolbuk2]

I have an additional question. For choices A, B, and E, there is a phrase that says "green auroras of the Northern Lights in cities" (or similar to this). I take that to mean that the auroras are physically in the cities themselves and I eliminated the choices. Am I reading too much into this or is it assumed that the meaning of the phrase is that people will be able to see them while physically in the cities?

[RonPurewal]

I have an additional question. For choices A, B, and E, there is a phrase that says "green auroras of the Northern Lights in cities" (or similar to this). I take that to mean that the auroras are physically in the cities themselves and I eliminated the choices. Am I reading too much into this or is it assumed that the meaning of the phrase is that people will be able to see them while physically in the cities?

for B--which quite plainly says that people can see the auroras in the cities themselves--this is a solid objection.

for A it's possibly an objection, but only a flimsy one, since "visible in cities" describes where the auroras can be seen, and not necessarily where they actually are.
the real objection there is that "visible from" is much less ambiguous.

for E this is not an objection at all, because "people in cities" is %100 accurate.