Choose the correct alternative.

The shindig has been put on by Facebook for the benefit of delegates _______ its F8 conference. The event, which _______ most years since 2007, _______ as a means to win over the developer community and _______ a comprehensive and highly engineered launchpad for the company’s annual plans. Many of the attendees have paid a lot of money to find out how they can integrate their own digital products with Facebook to carve out some kind of presence _______ its enormous audience – and there’s booze and entertainment thrown in.

https://www.theguardian.com/technology/2016/apr/23/facebook-global-takeover-f8-conference-messenger-chatbots