1) The word "book" contains two vowels: O and O.

2) Kim Kardashian West is an American media personality, businesswoman, and socialite. She gained fame through reality television show "Keeping Up with the Kardashians" and has built a successful brand empire encompassing fashion, beauty, and other ventures.

3) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.

4) The Iguazu Falls, located on the border between Argentina and Brazil, is a majestic waterfall system consisting of numerous cascades and islets. It is a UNESCO World Heritage site and one of the most impressive natural wonders in the world, attracting millions of visitors each year.