Rewrite the sentences using the third conditional. 1 Mark Zuckerberg did well at school, so he went to university. If __________ university. 2 The university didn't have a social networking site, so Mark invented one. Mark __________ one. 3 Facemash wasn't a success because the university didn't approve of it. If __________ a success. 4 Mark invented Thefacebook because he wasn't happy with the university's decision. Mark __________ the university's decision. 5 Thefacebook became so popular that thousands of Harvard students joined it. If __________ it. 6 Facebook opened to the public in 2006, becoming the biggest social networking site in the world. If __________ social networking site in the world.