An organic compound has molecular formula C9H18. It is a saturated hydrocarbon and all its hydrogen atoms are identical. Its structural formula can be:
a) CH₃(CH₂)7CH₃
b) CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₃
c) CH₃CH₂CH(CH₃)CH₂CH₂CH₂CH₃
d) CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₃