Which of the following statements is incorrect?

• A
  $CH_3-CH_2-CH_2-OH$ and $CH_3-CH(OH)-CH_3$ are a pair of functional group isomers.
• B
  $CH_3-CH_2-OH$ and $CH_3-O-CH_3$ are functional isomers.
• C
  $CH_3-CH_2-CH_2-OH$ and $CH_3-O-CH_2-CH_3$ are not position isomers.
• D
  $CH_3-CH_2-COOH$ and $HCOOCH_2CH_3$ are functional group isomers.