The data collected by weather airplanes that fly into the heart of a hurricane are useful mainly for gauging the storm’s structure and strength,
not for the speed and the path of their movement.The question has been answered multiple time, but let's not focus on grammar, parallelism and other GMAT trick, and try to analyse the question entirely from meaning perspective one more time with me.
Analysis 1:
The data
collected by weather airplanes that fly into the heart of a hurricane are useful
mainly for
gauging the storm’s structure and strength, not for the speed and the path of their movement.Let's focus on non-underlined portion -
The data are useful for SOMETHING - we need to figure out what is that SOMETHING now.
That SOMETHING is "
gauging/measuring/calculating the storm’s structure and strength, not
gauging/measuring/calculating the speed and the path
Hence, The data are useful for gauging the storm’s structure and strength, not the speed and the path
Analysis 2:
The data
collected by weather airplanes that fly into the heart of a hurricane are useful
mainly for gauging the storm’s structure and strength, not for the speed and the path of their movement.Let's focus on non-underlined portion -
The data are useful - now we need to see what comes after useful.
If we consider the first part where "data are useful FOR gauging the storm’s structure and strength", in the second part we should write - "data are not useful FOR <GAUGING/MEASURING/CALCULATING> the speed and the path".
Logically and considering the meaning, it doesn't make sense that data can be used for the speed and the path directly. Data can be used only to ESTIMATE/GAUGE/CALCULATE the speed and path, the way data was used to ESTIMATE/GAUGE/CALCULATE structure and strength.
Hence, I would go ahead with my analysis 1 and answer choice C.
Thanks and please help to improve this (if my logic is incorrect).