500
How can this thesis be fixed?
The biggest challenges that Cleveland needs to focus on in the coming years is the retention of highly educated graduates, preventing more suburban sprawl, and corruption of public officials, which needs to end.
This sentence lacks parallel structure.
The biggest challenges that Cleveland needs to focus on in the coming years ARE
-retain[ING] highly educated graduates
-prevent[ING] more suburban sprawl, and
-end[ING] the corruption of public officials.