The police questioned the hotel staff and guests. They could not establish the cause of the fire.<br/><br/>In joining the above sentences, which of the following sentences is correct? <br/><br/>1. Despite the police questioning the hotel staff and guests, they could not establish the cause of the fire. <br/><br/>2. Despite the police's questioning the hotel staff and guests, they could not establish the cause of the fire. <br/><br/>3. Despite questioning the hotel staff and guests, the police could not establish the cause of the fire. <br/><br/>Many thanks.