Which of the following is not a valid resonance structure of the other three?

Step-by-step solution

Let us analyze the given structures by determining the position of atoms and the number of hydrogen atoms at each carbon. Structure (A) is 3-methylenehexa-1,4-diene. The carbon skeleton and hydrogen count are as follows: C ₁ H ₂= C ₂ H - C ₃(= C ₇ H ₂)- C ₄ H = C ₅ H - C ₆ H ₃ Now, let us evaluate the other structures to see if they are valid resonance structures of (A). Recall that resonance structures involve only the delocalization of electrons or lone pairs; the position of all atoms (including hydrogens) must