Simple propositions: Propositions that do not contain other propositions. They can only be analyzed as different terms, and they can no longer be analyzed as other propositions, so they are also called "atomic propositions". Which of the following is not a simple proposition? ['Xiaoming and Xiaohong are friends.', 'Life is movement.', 'Rolling the dice with a 4 point probability is 1/6.', 'Xiao Zhang is both tall and fat.']