You will be given a statement and two events in Croatian. The events are either something that can be caused by the statement, or they are something that might have caused the statement. If they can be consequences of the statement, answer with "effect", else answer with "cause".
Q: Statement: Dječaka su boljela leđa.
Choice 1: Ruksak mu je bio otvoren.
Choice 2: Ruksak mu je bio težak.
A: 
cause