Correct Answer - d
a.
They are not in one plane because `C_(2)` is sp - hybridised and is linear, whereas `C_(1)` and `C_(3)` are s`p_(2)-` hybridised.
So they will show dipole moment.
But
They are in one plane and will not show dipole moment.
Rule `:` Even number of double bonds with two different groups on terminal `C` atoms are resolvable `(O,A.)`, but odd number of double bonds with two different or same groups on terminal `C` atoms are irresolvable `(O.I.A.)`.