The planet Earth is 4,600 million years old. It is difficult for us to think about such an enormous length of time because it has little meaning for us. We can, however, simplify the idea to make it more understandable. We can compare the planet Earth to a person of forty-six years of age. Nothing is known about the first seven years of this person’s life. Very little information exists about the middle period either. It was only at the age of forty-two that the Earth began to flower. Dinosaurs and great reptiles did not appear until one year ago, when the planet was forty-five. Mammals only arrived eight month ago. In the middle of last week, man-like apes became ape-like men and began to communicate with each other. Last weekend, the Ice Age covered the Earth. Modern man has only been around for four hours. During the last hour man discovered agriculture. The Industrial Revolution and the rise of large cities began just sixty seconds ago. During that short time, modern man has made a rubbish tip of the Earth. In one minutes, he has increased his numbers to terrible proportions, and has caused the death of hundred of species of animals. He has robbed and destroyed the planet in his search for fuels. Now he stands, like a violent, spoilt child, delighted at the speed of his rise to power, on the edge of the final mass destruction and of killing all the life which exists in the solar system.   46. According to the passage, ____.        a. our planet is over 4,600 million years old        b. dinosaurs and great reptiles appeared during the Ice Age        c. man-like apes can communicate with each other        d. we know nothing about the first period of the life of our planet   47. In the context of the passage, what does the word “flower” mean?        a. to develop fully                                                   b. to produce flowers        c. to become famous                                               d. to become more successful   48. Which of the following is not true?        a. Modern man is destroying the Earth        b. Modern man has caused the distinction of hundreds of species of animals        c. We know very little about the middle period of the Earth’s life        d. We now live in a time called the Ice Age   49. From reading the passage, it seems that the author ____ .         a. approves modern man’s activities        b. thinks that modern man has no right to destroy the Earth        c. thinks that modern man has been the most successful animal        d. says that modern man should kill all life which exists in the solar system   50. The tone of the last paragraph is best described as ____ .         a. somewhat hopeful                         b. pessimistic        c. militant                                          d. overly optimistic