18. Fill in the blanks with the modal verbs as per the instructions given in brackets:
a. We _________ aim at noble goals. (Desirability)
b. You _________ leave the office early today. (Permission)
c. He has sent the message that he __________ be late. (Possibility)
d. She _________ tell her father the whole truth. (Absence of Courage)
e. _______ I stay here tonight?? said the stranger. (Polite request)
f. I _________ run a mile when I was young. (Ability in the past)