He can't have been ill是现在完成时?

He can't have been ill是现在完成时? He can't have been ill. They can't have been doing thier homework.have been 是现在完成时,但 must have been和can't have been和现在完成时有没有联系啊 He must have been ill,___ he? can't have been,must have been 结构里是不是不要把have been当现在完成时看,就把它 he can't have been Danish.he must have been Swedish. He can't have been.He must have been.不是说单三用has吗? he can't haue been a dcntist.he must have been a doctor. 关于现在完成时have been 现在完成时的have been can't have been和must have been