The correct answer is A. Acetylene.
A double bond is a covalent bond between two atoms that share two pairs of electrons. It is represented by two lines between the atoms.
Acetylene is a hydrocarbon with the chemical formula $C_2H_2$. It is a colorless, flammable gas with a garlic-like odor. Acetylene is the simplest alkyne, and it is the simplest hydrocarbon with a triple bond.
Ethene is a hydrocarbon with the chemical formula $C_2H_4$. It is a colorless, flammable gas with a sweet odor. Ethene is the simplest alkene, and it is the simplest hydrocarbon with a double bond.
Ethane is a hydrocarbon with the chemical formula $C_2H_6$. It is a colorless, odorless, flammable gas. Ethane is the simplest alkane, and it is the simplest hydrocarbon with only single bonds.
Methane is a hydrocarbon with the chemical formula $CH_4$. It is a colorless, odorless, flammable gas. Methane is the simplest alkane, and it is the simplest hydrocarbon with only single bonds.
Therefore, the only compound that has a double bond is acetylene.