I realized the value of my parents’ advice only wh en I myself became a parent.   

A. It was only when I realized the va lue of my parents’ advice I m yself became a parent.  

B.  It was only when I myself became a  parent did I realize the val ue of my parents’ advice. 

C. Only when I myself became a pare nt did I realize the value of m y parents’ advice.  

D. Only when I myself became a parent that I realized the value of my parents’ advice.