Passage: Two styles of boats are used in this sport: canoes with 1 or 2 canoers and kayaks with 1, 2 or 4 kayakers.  This leads to the name designation of each event.  For example, "C-1" is a canoe singles event and "K-2" is a kayak doubles event.  Races are usually 500 metres or 1000 metres long, although there were also 10 km events from 1936 to 1956. On 13 August 2009, it was announced by the International Canoe Federation that the men's 500 m events would be replaced at the 2012 Summer Olympics by 200 m events with one of them being K-1 200 m for the women. The other events for men at 200 m will be C-1, K-1, and K-2. This was confirmed at their 2009 Board of Directors meeting in Windsor, Berkshire, Great Britain on 5 December 2009.

Question: Kayaks can have as many as how many people in them?
4