He isn't at school .I think he ( )be ill.can,shall,must,has

He isn't at school .I think he ( )be ill.can,shall,must,has he isn't at school.i think he ------be ill A.has to B.shall he isn't at school i think he -----be ill He isn't in the school .I think he_____be ill.A.must.B.can C He isn't in the school ,I think he ___ be ill . He must be ill ,for he isn't here. He isn't in the school .I think he __be ill. -Tom isn't at school today.He ____ ill at home. -I'm not sur Tony isn't at school because he is ill. I don't think he can （ ）at school. He hasn't come to school today.I think he ( ) be ill. He isn't at school today.I think he _____be will