Answer: Marcos cumple años en septiembre.
Explanation: We need to complete the sentence "Marcos _____ años en Septiembre."
A rough translation of this is:
"Marcos ____ birthday in September"
There is not an actual direct relation between both sentences, and the word that completes the Spanish one is "cumple"
Wich means that in September, Marcos has "one year more in his life" if you want to phrase this way.
