I can’t remember how the tune goes, ______ I’ll recognize it when I hear it[ ]

下列各句中，没有语病、句意明确的一句是

Is this the reason ______ at the meeting for his carelessness in his work? [ ]

I don’t think the risk they took ______ the poisonous snake is worthwhile

My parents and I_______ interested in films. _______often go to the cinema.