Choose the correct option. They ____ in the park and played football there.

The sentence requires a plural verb to agree with the subject "They". Since the action is in the past and the sentence implies a state or action, "were" is the correct choice. "Wasn't" and "was" are singular. "Weren't" would be used if the sentence was negative, but the context of playing football suggests a positive statement.

The correct option is were.