a hard nut
无知无觉的人
A: Bob refused all his classmates' invitations.
A: 鲍勃拒绝了班上所有人的邀请。
B: I really couldn't understand him.
B: 他这个人我真不明白。
A: He's surely a hard nut,nobody likes approaching him.
A：他真是个脑子不开窍的人，没人愿意接近他。
B: We'd better also leave him alone.
B：我们最好也别惹他。