I agree that the longer the symbol is, the larger the amount of delay spread a system will be able to tolerate, as explained in the study guide.
If you say that "an older technology with a lower data rate may have more difficulty with multipath than a newer technology with a higher data rate", this means that a low data rate FHSS system will have more difficulty that a higher rate DSSS system.
Is this true?
The author of the question gives D as the answer.
No, I only mean to suggest the possibility.
It is also possible that I am missing the boat here on some other aspect of multipath that would lead to answer D being the correct one.
I hope this helps. Thanks. /criss