Step 3: For each of the sentences below, select the choice that uses verb tenses correctly. In general, verb tenses should be consistent within a sentence. There are some instances, however, when it is correct to switch tenses in the same sentence. If the original sentence is correct, select "no change."

		1. Some volcanic eruptions are explosive, such as the one at Mount St. Helens, and some were less severe, like the relatively gentle flow of lava at Mount Kilauea on the island of Hawaii.
		2. The difference, according to some scientists, is the amount of gas in the molten rock, or magma, within the volcano; the more gas there is within the magma, the more explosive is the eruption.
		3. Volcanoes that had a lot of water and carbon dioxide in their magma are usually more explosive, like a bottle of champagne with its cork suddenly pulled out.
		4. To get a closer look at how this worked, some scientists recently collect rock samples at Mount Vesuvius in Italy, which erupted in the year 79 C.E., destroying the towns of Pompeii and Herculaneum.
		5. This eruption killed more than 3,000 people and blasted a cubic mile of ash high into the sky.
		6. In currently ongoing experiments, the scientists insert into a small capsule crushed rock from Mount Vesuvius and other gases that they knew are still present in the original magma.
		7. The scientists placed the capsule into a heated pressure vessel, then change the temperatures and pressures inside the vessel to see how the magma may react during an eruption.
		8. Just before the Mount Vesuvius eruption, the temperature inside the magma chamber goes up to about 2,000 degrees Fahrenheit, and the pressure was about 22,000 pounds per square inch, similar to the pressure four miles underground.
		9. Scientists worldwide continually kept watch on active volcanoes with satellites and ground instruments, trying to see how much gas the volcanoes emit.
		10. They hoped to compare the gas emissions from satellites and instruments with the findings from their laboratory-simulated "Mount Vesuvius" and then improve predictions of when and how powerful future eruptions will be.
		Step 4: Now that you have practiced using verb tenses correctly and, when appropriate, consistently, think about an act of nature that you have experienced or can imagine, such as an earthquake, a severe thunderstorm, a heat wave, or a blizzard. Then write a paragraph about it in the box below. When you finish, check to make sure your verb tense is consistent throughout your writing, and make any necessary corrections.   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
Answer choices in this exercise are randomized and will appear in a different order each time the page is loaded.