Which solution turns litmus paper red

Examine the false statement. compounds are the smallest unit of an element that occur most commonly in nature. select the rewording of the statement that is true. a: atoms are the smallest unit of an element that commonly occur in nature. b: molecules are the smallest unit of an element or compound that commonly occur in nature. c: molecules are the smallest unit of a compound that occur on the periodic table. d: compounds are the smallest unit of an element that occur on the periodic table