I am regretful about what has happened.

What about this danger of war, which is making us all shake in our shoes at present？ I am

—Our son has picked up some bad habits recently, and I am really worried about it.— .A

I feel regret about what’s happened.

I am 【regretful 】about what has happened.A.sorry

I feel 【regret 】about what’s happened.A.sorry B.d

I don’t regret ________ her what I thought about her proposal even if it upset her.