I believe the word that best fit in is CLOSE. They all mean to close but in different forms. Cerramos because the ending of the word cerramos is in a nosotros form. It should be in nosotros form because it's saying "we"(nosotros).
yo: cierro tu: ci<span>erras el/ella/Ud: </span>ci<span>erra nosotros: </span><span>cerramos </span>ellos/ellas/Uds: ci<span>erran </span><span> SO THE ANSWER IS CERRAMOS