The moment he had said this,he_____(regret) it.

The moment he had said this,he_____(regret) it.
The moment he had said this,he_____(regret) it.

The moment he had said this,he_____(regret) it.
regretted 这是用过去式陈述过去的事实,所以用一般过去.

regretted

has regretted