Starting in 1972, lightning fires in Yellowstone National Park ________to take their natural course unless they threatened park facilities.

Of the two new teachers, one is experienced and ________.

The 'Consumers Price Index' lists ________.

Nerve impulses ________ to the brain at a speed of about one hundred yards per second.

In excess of 80 percent of the UN's budget is used ________ the economic development of member nations.

Bacterial spores germinate and sprout ________ favorable conditions of temperature and food supply.

In the 1960s, due in part to the invention of air conditioning, the population of the United States ________ a dramatic geographical shift southward.

One of the most influential Virginians of colonial times, ________ in England.

High and low atmospheric pressure systems are ________ cause changing weather patterns.

Jupiter ________ the largest planet in the Solar System.