Question

Which is an element? ... air ...carbon dioxide ...hydrogen ...water Description

Answer 1

The answer is Hydrogen.

Hydrogen can be found in the periodic table. There other choices are not element but compounds, which is a molecule made of more than ONE element.

Air is a mixture of gas molecules
Carbon dioxide is CO2
Water is H2O

So as you can see, they se al made of different elements

Answer 2

All Elements are obtained in the periodic table & water is Not an element it is a compound.