"Passano sette lunghi anni."

[Koolkaren]

Can this also mean ' They spend seven long years', or would this use a different verb?

[marziotta]

Yes and no. It could mean that, but then you should say WHAT they do in those seven long years.

"Passano sette lunghi anni a ricercare, senza trovare la risposta."

Does it make any sense in English to say to spend time without saying what for? (I ask, I don't know!) :)

[Koolkaren]

You're right. Unless a question had been asked making the acitivity clear, the sentence would say what they spent the seven years doing.

[katebailward]

Yes, but equally there are plenty of other examples of sentence fragments throughout the exercises here, so I'm not sure why this one isn't accepted when others are.