The following names are incorrect. Draw the structure of the compound and provide the correct IUPAC name.
(a) H₃C-CH(CH₃)=CH₂, 2-methylpropene
(b) H₂C(CH₃)-C(CH₃)₂, 2,3-dimethylbutane
(c) H₃C-CH₂-CH₂-C(CH₃)₃, 3-ethylhexane
(d) H₃C-CH₂-C(CH₃)₂, 2-methylpentane