The cylindrical shape of an alkyne is due to the fact that it has (reference to the functional group only)

• A

  Three sigma (C-C) bonds

• B

  1 Sigma (C-C) and Two pie (C-C) bonds 

• C

  2 Sigma (C-C) bonds & 1 pie (C-C) bonds 

• D

  3 $\sigma$C-C) Bonds