Answer:
alkene.
Step-by-step explanation:
Remember that C can be bonded 4 times and H just once. You can realize that the structure of CH2CH2 is the following:
This structure has a double bond between carbon and carbon atoms.
You can note that this is an alkene: an alkene is a hydrocarbon with one or more carbon-carbon double covalent bonds.
The answer would be alkene.