Answer
$C_2H_5$ is the empirical formula.
Work Step by Step
The diagram shows bonds that are
$red-black-red$ and $white-red-white$
It is stated that the diagram includes $H_2O$ and $CO_2$. Oxygen must be red since it appears in both compounds. This leaves carbon as black and hydrogen as white, based on the ratios in the compounds.
Hydrocarbon is composed of hydrogen and carbon. There are 10 white/hydrogen atoms in the diagram and 4 black/carbon atoms. This can be written as $C_4H_{10}$ and reduced to siimplest terms with division by 2 as $C_2H_5$.
