He ______ be sitting at the gate, waiting for his lost son.
I can't say which wine is best-it's a (n) ___ of personal taste.
---May I ask for a leave,sir? ---sorry,the meeting _____ no absence.
At the beginning of class, the noise of desks _____ could be heard outside the classroom.
This washing machine is environmentally friendly because it uses _____water and electricity than _ ___models.
__ __ so much trouble, we failed to complete the task on time.