That depends. there are 2 possible answers.
H
C - C = C - H gives a different answer on the right than on the left.
One the left side, the second Carbon is attached to a double bond and has but one hydrogen attached to it.
The Carbon on the right of the double bond has 2
H
C- C = C - H
H
I'm not sure what you should put. It's one of those things that I would repeat my argument and submit it.
