$\text{4HC}\equiv \text{CH}\underset{\text{THF/pressure}}{\overset{{\text{Anhydrous Ni(CN)}}_{\text{2}}}{\to }}\text{ A}$, In this reaction the compound A is?

• A

   Ethylbenzene

• B

  Cyclooctatetraene

• C

  Benzene

• D

   Cyclobutadiene