Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

Columbus crossed the Atlantic Ocean three times. His first voyage brought him fame and popularity - he discovered a new continent. But he had enemies who wanted to get rid of him. On his second voyage the Government of the country that Columbus himself discovered threw him into prison.

He was sent back to Spain as a prisoner. But Columbus succeeded in proving that the lies his enemies spread about him were untrue, and the Spanish Government gave him four ships to start on a new voyage. But this third voyage was unfortunate from the beginning. The ships were met by terrible storms and the time he reached the shores of Haiti, Columbus lost three of them. The remaining ship was about to go down when Columbus reached the island.

It took Columbus almost a year to return to Spain. He was unhappy, disappointed and broken in health. Worst of all, everyone forgot his achievements. He died in poverty in 1506 without knowing that he discovered a new world. Before Columbus died, another traveller named Amerigo Vespussi returned to Spain. He travelled along the coast of the land that Columbus discovered, and he proved that it was not the coast of India, as Columbus thought, but unknown continent.

For a long time the new continent was called the New World. But at last, they decided to name it America, in honour of Amerigo, whose voyage showed it was not India. America was discovered by Columbus in 1492. It was named America in 1506, the year in which Columbus died.

Most of the scientists agree that human (25)______ is the main cause of the problem.