28. In the 19th century, it _ two or three months to cross North America by covered wagon. The trip - very rough and often dangerous.

a. took / was

(b, had taken / had been

c. took / had been

d. had taken / was

What are the primary elements that make up the Earths atmosphere?

During the years of 1870-1900, most new immigrants to the United States came from: A) Europe B) Africa C) Australia D) South America

Many areas of the world produce just enough of an agricultural product to eat, but not enough to sell for profit. This is called A) subsistence farming. B) industrial farming. C) crop rotation. D) dry farming.

Both comet types come from some location near the ecliptic plane of the Solar System, but the long-period comets come from farther away. B.

Why do most earthquakes occur along tectonic plate boundaries?

Which body of water is found to the east of costa rica? a. el oc ano pacifico c. el mar del norte b. el oc ano atlantico d. el mar caribe

How old is the milky way galaxy?

Describe the Great Barrier Reef. Why is this site considered one of the world's most important ecosystems?

The diameter of a circle is 5.5m. Find the area of the circle. Give the exact value

Which of the following clouds has the highest base? a. stratocumulus b. cirrocumulus c. altocumulus d. nimbostratus