Which of the following represents a valid linear programming constraint? $($c$)$ Rogers This copywritten question may not be copied, photographed, screenshot, or posted, without permission of the author, Dr$.$ Pamela Rogers, and Stephen F$.$ Austin State University.

A$)(2x)(7Y)500$

B$)2x7xY$

C$)2x^2+7Y50$

D$)2x+7Y100$