GMAT Sentence Correction (SC) | The primary catalyst fueling the rapid spread of wind farms across the

"requiring" in the original sentence modifies "combination" and not the closest noun. How can "federal tax incentives" require anything? The intended meaning is, a combination of federal tax incentives and something else (state mandates ... energy production) has caused the rapid spread of wind farms.

The logical antecedent of "Their" is "utilities" and not to "'federal tax incentives and state mandates'". How "federal tax incentives