Question

los jugadores ( estaban / estuvieron ) contentos de ganar el juego.

Explanation:

To determine the correct verb, we analyze the context. "Estar contento" (to be happy) in the preterite imperfect tense for "ellos" (los jugadores) is "estaban". "Estuvieron" is preterite perfect, used for completed actions, but "contentos de ganar" describes a state during the past, so imperfect is appropriate.

Answer:

estaban