1)I should have studied harder.
He studied/didn't study hard.
2) I should have joined the school band.
She joined/didn't join the band.
3) I shouldn't have been so mean to Jimmy.
He was/wasn't mean to Jimmy.
4) I shouldn't have chosen physics and chemistry.
She chose/ didn't choose physics.
Answers & Comments
Verified answer
1) I should have studied harder.
He didn't study hard.
2) I should have joined the school band.
She didn't join the band.
3) I shouldn't have been so mean to Jimmy.
He was mean to Jimmy.
4) I shouldn't have chosen physics and chemistry.
She chose physics.