Refer to the input text as context and select the correct relationship between 'Berkshire Hathaway' and 'Warren Buffett' from the available options.
Options: currency, platform, distributed by, chief executive officer

It should come as no surprise that the most popular of these portfolios is that of renowned investor Warren Buffett , CEO of Berkshire Hathaway ( BRK.B ) and one of the richest people in the world.
chief executive officer