JOHN WASN ' T AT WORK YERTERDAY. HE ...A. MUST HAVE BEEN ILL. B. M...

12. - DE HSG ANH VAN 9 CO DAP AN 4
DE HSG ANH VAN 9 CO DAP AN 4

12. John wasn ' t at work yerterday. He ...

a. must have been ill. b. must be ill.

c. must have ill . d. must to be ill.