Answer: Formula is C4H8O. In every branch of line formula there are Carbon atom. Carbon makes 4 bonds so In branch left in which two CH3-groups are attached there are also an Hydrogen aton which is not shown.
Explanation: Molecule is organic, it is classified as aldehyde.
Hydrocarbons contains only Carbon and Hydrogen atoms, Organic molecules can contain also other atoms.
Reactions of aldehydes are reduction to alcoholes or oxidation to carboxylic acids. It can not for a polymer.