Water is the only non-element in those choices. There are many ways to figure this out. If you had the periodic table accessible to you, just look on there. If you don't see something on it, it isn't an element. There are only 118 known elements in the world as of today. Another way to do it is to look at the hints that each of their symbols give you. The chemical symbol for hydrogen is H, water is H2O, argon is Ar, and uranium is U. The start of every symbol is a capital letter, so each element only has one capital letter. If there is more than one capital letter in a symbol, then you know there is more than one element inside of that chemical, meaning that it cannot be a pure element, and must be a compound or mixture. Hope that helped! Can I please have a brainliest? :)
