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 before it came down in torrents.
C.I regret having watered the garden before it came down in torrents.
D.If it had came down in torrents, I wouldn’t have watered the garden.