关于现在完成时的用法he can't be ill he can't have been ill .哎 弄不懂这两者到底

He can't have been ill是现在完成时? He can't have been ill. He isn't at school .I think he ( )be ill.can,shall,must,has He can’t come because of _____ 【ill】 Mike ill today. He can't go to school改错 He must have been ill,___ he? 看答句写问句 ( No,he can't.( I can see four.( Wei Fang is ill at h Beause he is ill,so he can't go to school today. He can't come because he is ill. 改同意句 Tom’s father has a bad ______ (ill),so he can’t go to work t he isn't at school i think he -----be ill He must be ill ,for he isn't here.