Names of some compounds are given. Which one is not in $IUPAC$ system?

• A
  $CH_3-CH(OH)-CH(CH_3)_2$ $(3-\text{Methylbutan-}2-\text{ol})$
• B
  $CH_3-C\equiv C-CH(CH_3)_2$ $(4-\text{Methylpent-}2-\text{yne})$
• C
  $CH_3-CH_2-C(=CH_2)-CH(CH_3)-CH_2-CH_3$ $(2-\text{Ethyl-}3-\text{methylbut-}1-\text{ene})$
• D
  $CH_3-CH_2-CH_2-CH(C_2H_5)-CH(CH_3)-CH_2-CH_3$ $(3-\text{Methyl-}4-\text{ethylheptane})$