Acetylene has garlic odour due to the presence of impurities of

• A

  ${\mathrm{NH}}_3$

• B

  ${\mathrm{PH}}_3+{\mathrm{H}}_2\mathrm{S}$

• C

  ${\mathrm{ASH}}_3$

• D

  ${\mathrm{NH}}_3+{\mathrm{ASH}}_3$