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.
Every year about two million people visit Mount Rushmore, were the faces of four U.S presidents were carved in granite by sculptor Gutzon Borglum and his son, the late Lincoln Borglum. The creation of the Mount Rushmore monument Line took 14 years – from 1927 to 1941 – and nearly a million dollars. There were times when money was difficult to come by and many people were jobless. To move more than 400,000 tons of rock, Borglum hired laid-off workers from the closed-down mines in the Black Hills area. He taught these men to dynamite, drill, carve, and finish the granite as they were hanging in midair in his specially devised chairs, which had many safety features. Borglum was proud of the fact that no workers were killed or severely injured during the years of blasting and carving.
During the carving, many changes in original design had to be made to keep the carved heads free of large fissures that were uncovered. However, not all the cracks could be avoided, so Borglum concocted a mixture of granite dust, white lead, and linseed oil to fill them.
Every winter, water from melting snows gets into the fissures and expands as it freezes, making the fissures bigger. Consequently, every autumn maintenance work is done to refill the cracks. The repairers swing out in space over a 500-foot drop and fix the monument with the same mixture that Borglum used to preserve this national monument for future generations
Today, Mount Rushmore needs to be _________
A. protected from air pollution
B. polished for tourists
C. restored during the winter
D. repaired periodically
