Which one of the following is true about the molecule C₁-C₂ and C₃-C₄?
a) C₁-C₂ and C₃-C₄ are of the same length
b) C₁-C₂ bond is shorter than C₃-C₄
c) C₁-C₂ and C3-C4 are of different lengths
d) C₁-C₂ bond is longer than C₃-C₄