If in an allene system, nodal plane of first $\mathrm{\pi }$-bond and last $\mathrm{\pi }$-bond are in same plane then select the correct statement.

Allene will be planar :- Polarity is limited by symmetry considerations; only Cn, Cnv, and Cs molecules can be polar and allene is D2d. Allene has elements of symmetry which are perpendicular. 

Total no. of $\mathrm{\pi }$-bonds will be in odd number :- Even numbers and odd numbers are defined only for integers, as an integer is even when it is of form 2k, where k is an integer, an integer is odd when it is of form 2p+1, where p is an integer.

Total no. of carbons in allene will be in even number :-Allenes having even no of pi bonds are optically active if the groups present on a carbon are not same .And this is due to lack of plane of symmetry and centre of symmetry in the molecule