I needn’t have watered the garden because it came down in torrents after that.

A. If only I had watered the garden before it came down in torrents.

B. It's a pity I had watered the garden after it came down in torrents.

C. I regret having watered the garden before it came down in torrents.

D. If it had come down in torrents, I wouldn’t have watered the garden.