He's out of his office, he [ ] be at the conference [ a) can b) would c) must ]	must
I'm afraid you [ ] ring later [ a) should b) can c) would ]	should
[ ] I leave a message? (hint: you want to be polite) [ a) Must b) Can c) May ]	May
I'm sorry, [ ] you please reschedule our appointment? [ a) could b) should c) must ]	could
[ ] you like to call back? (hint: you want to be polite) [ a) Can b) Would c) Could ]	Would