I regret that I did not study hard at school.
I regret that I did not study hard at school.
私は学校で一生懸命けんめい勉強しなかったことを後悔しています.
I regret to say that I cannot help you.
I regret to say that I cannot help you.
(お助けできないと言うことを残念に思う)残念ながら君を助けてあげられない.
⦣ I'm sorry to say that ~. より改まった言い方.