Answer: ethene
Step-by-step explanation:
The representation of the hydrocarbon is:
H H
\ /
C = C
/ \
H H
So, the double C bond means it is an alkene.
The number of carbon atoms in the molecule is named with the proper prefix:
propa - is used for 3 carbon atoms
penta - is used for 5 carbon atoms
but - is used for 4 carbon atoms
etha - is use for 2 carbon atoms.
Therefore that alkene is name ethene