Final answer:
Ethene (C2H4) is the compound among the given options that contain a double bond.
Step-by-step explanation:
The compound that contains a double bond among the choices provided is ethene (C2H4). Ethene consists of two carbon atoms connected by a double bond, with each carbon atom also bound to two hydrogen atoms. Compounds such as ammonia (NH3), methane (CH4), and diatomic chlorine (Cl2) consist only of single bonds between their constituent atoms. Methane, for instance, has a central carbon atom with four single bonds to hydrogen atoms, forming a tetrahedral shape. Therefore, when comparing methane, ammonia, chlorine, and ethene, only ethene possesses a carbon-carbon double bond.