I have been living in the United States for 20 years, but seldom ________ so lonely as now.
He is working hard, ______will make him pass the final exam.
The reason ______he didn't come was ______he was ill.
This machine, ______for many years, is still working perfectly.
This is the reason ______he didn't come to the meeting.
The way ______he looks at problems is wrong.