GMAT Sentence Correction (SC) | Re: To map Earth's interior, geologists use a network of seismometers to

To map Earth's interior, geologists use a network of seismometers to chart seismic waves that originate in the earth's crust and ricochet around itsinterior, most rapidly traveling through cold, dense regions and slower through hotter rocks.

A.interior, most rapidly traveling through cold, dense regions and slower : what is most rapidly travelling thru cold? not sure move on!
B. interior, which travel most rapidly through cold, dense regions, and more slowly interior travel? weird!
C. interior, traveling
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