Read the text and complete it with the correct form of the verb in brackets. Use the other words to help you.

Researchers (1) have just carried out a study to discover what makes us happy. 'We (2) spoke to a wide range of people last week,' said a research spokesperson. 'Even though we (3) haven't yet collated all the results, we (4) have already made some important findings.' Perhaps researchers (5) will find the key to happiness after all.