Re attack after “noping” a chain of attacks
As I understand it, a Nope card cancels only a single card (or one action with multiple cards in the case of a special combo) so player D will play 6 turns.
From the rules:

Stop any action except for an Exploding Kitten or a Defuse Card. Imagine that any card beneath a Nope Card never existed.
You can play a Nope Card at any time before an action has begun, even if it’s not your turn. Any cards that have been noped are lost. Leave them in the Discard Pile. You can even play a Nope on a SPECIAL COMBO