Write structural formulas for all of the possible structural isomers of hex-1-ene that can be formed by moving the position of the double bond.
a) CH₃CH=CHCH₂CH₂CH₃
b) CH₃CH₂CH=CHCH₂CH₃
c) CH₃CH₂CH₂CH=CHCH₃
d) CH₃CH₂CH₂CH₂CH=CH₂