be on sb idiom mainly US informal
用于表述负责某事的某人
used when saying who is responsible for something
If he doesn't like it, then it's on him to change it. 如果他不喜欢，那么他有责任来改变它。
"It's too much." "That's on you. I offered to help but you said no." “这太过分了。”“这是你的责任。我曾想帮忙，但你拒绝了。”