A:Hello,I've got something to do,may I ask for a leave?
B:Oh,I'm so sorry that I can't permit you at this moment.
A; Why?I really want to leave!
B:Because we all need you to stay here,and without you we can't finish anything.
A:But you said that i am free here.
B;OK.You can leave,but make sure you'll be back on time.