Which of the following statements are wrong?

• A

  Isobutane and n-butane are chain isomers.

• B

  Ethyl cyanide and ethyl isocyanide are functional isomers.

• C

  $\mathrm{H}-\mathrm{C}\equiv \mathrm{N}\text{ and }\mathrm{H}-\stackrel{\oplus }{\mathrm{N}}\equiv \stackrel{\ominus }{\mathrm{C}}$

• D

  Maleic and fumaric acids are enantiomers.