Sentence correction, problem set 6, question 9

[Adilka]

Hello,

In this question, am I correct to end it with

"... but which has fewer calories than an equivalent amount of corn syrup"

as opposed to the suggested version

"... but which has fewer calories than DOES an equivalent amount of corn syrup"

I mean, am i violating any grammatical rules by removing "does" from the sentence?

Thank you very much for your response.

[JonathanSchneider]

You need to incude the "does" only when the comparison would otherwise be unclear. This lack of clarity can occur in one of two ways: you have another item in between the two that you mean to compare, thus making the comparison unclear; or you have so many words between the two pieces that the reader cannot be positive what is intended. In this case, because you have a modifier, "but which...", it is likely that you could have a lack of clarity due to too many words between your compared points. However, in general you do not need the word "does" whenever the comparison is still clear without it.