Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 45 to 50.

As many as one thousand years ago in the Southwest, the Hopi and Zuni Indians of North America were building with adobe-sun-baked brick plastered with mud. Their homes looked remarkably like modern apartment houses. Some were four stories high and contained quarters for perhaps a thousand people, along with storerooms for grain and other goods. These buildings were usually put up against cliffs, both to make construction easier and for defense against enemies. They were really villages in themselves, as later Spanish explorers must have realized since they called them “pueblos”, which is Spanish for towns. The people of the pueblos raised what are called “the three sisters” - corn, beans, and squash. They made excellent pottery and wove marvelous baskets, some so fine that they could hold water. The Southwest has always been a dry country, where water is scarce. The Hopi and Zuni brought water from streams to their fields and gardens through irrigation ditches. Water was so important that it played a major role in their religion. They developed elaborate ceremonies and religious rituals to bring rain. The way of life of less – settled groups was simpler and more strongly influenced by nature. Small tribes such as the Shoshone and Ute wandered the dry and mountainous lands between the Rocky Mountains and the Pacific Ocean. They gathered seeds and hunted small animals such as rabbits and snakes. In the Far North the ancestors of today’s Inuit hunted seals, walruses, and the great whales. They lived right on the frozen seas in shelters called igloos built of blocks of packed snow. When summer came, they fished for salmon and hunted the lordly caribou. The Cheyenne, Pawnee and Sioux tribes, known as the Plains Indians, lived on the grasslands between the Rocky Mountains and the Mississippi River. They hunted bison, commonly called the buffalo. Its meat was the chief food of these tribes, and its hide was used to make their clothing and the covering of their tents and tips.

The U.S. spent a lot of money trying to catch up with the Soviet Union in space . A. explorer B. exploring C. explore D. exploration