isomers of c4h8?

Question

i need the structural formula of the 5 isomers of C4H8 help pls

Answer 1

Assuming all are straight chain or branched structures:
One ring structure also has this formula. I tried to draw it last. (cyclobutane) Ignore the dotted line.

CH2=CH-CH2 -CH3
CH3-CH=CH-CH3
CH2=C(CH3)-CH3
CH3-C(CH3)=CH2
CH2-CH2
|...........|
CH2-CH2

Answer 2

Methylcyclopropane