Electronic devices such as iPods and headphones can do great harm to our hearing if _______ improperly.
—Why did you leave the water running in the sink? —My goodness! I guess I ____ to turn off the tap.
Washington, a state in the United States, was named _____ one of the greatest American presidents.
____ you ask many different questions will you acquire all the information you need to know.
Have you ever wondered why some of the smartest students in your class sometimes ____ failing exams?
The minister stressed that under no circumstances ____ the disabled to be looked down upon.