用情态动词或否定形式填空1、He ---be at home now ,because he called me from the office just now

用情态动词或否定形式填空1、He ---be at home now ,because he called me from the office just now
2、It ---be dangerous to smoke at the gas station.
3、He ------be the best student in his class ,for he never words hard .But if he words hard,he ----be .