Which of the following pairs is an example of position isomerism?

• A
  $CH_3-CH_2-CH_2-CH_3$ and $CH_3-CH(CH_3)-CH_3$
• B
  $CH_3-CH_2-CH=CH_2$ and $CH_3-CH=CH-CH_3$
• C
  $CH_3-CH_2-OH$ and $CH_3-O-CH_3$
• D
  $CH_3-C(CH_3)_2-CH_3$ and $CH_3-CH_2-CH_2-CH_2-CH_3$