Most people have wondered about the differences between horses and zebras. To understand the difference, you must first understand exactly what a horse is. The horse is a hoofed, plant-eating mammal of the family Equidae. This family includes domestic horses, wild horses, and zebras. All are swift, plains-dwelling herd animals who eat coarse grass. Horses, as we know them, evolved in North America and spread over the world. They were hunted by early humans and put to work by Asian nomads. Until the mid-20th century, horses were widely used for warfare, agriculture, and transportation. Today, most horses are used for farming purposes. Few modern horses roam wild.
On the other hand, most zebras live in open plains or brush country. Mountain zebras like rocky hillsides. Zebra herds on the Serengeti of East Africa can be as large as 200,000 zebras. All travel in family groups led by a stallion. The plains zebras usually mix with other grazing animals, such as wildebeest and antelopes.
You would have to look at the DNA of horses and zebras to understand their physical differences. Zebras and horses have very similar bodies except for their skins!

Which of the following helps the reader understand how the passage is organized?
A.
"On the other hand. . . ."
B.
". . .you must first understand. . . ."
C.
"Most people have wondered. . . ."
D.
"Few modern horses roam wild."