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. 

The White House, the official home of the United States president, was not built in time for George Washington to live in it. It was begun in 1792 and was ready for its first inhabitants. President and Mrs.John Adams, who moved in on November 1, 1800. When the Adamses moved in, the White House was not yet complete, and the Adamses suffered many inconveniences; for example, the main staircase was incomplete, which hindered movement from floor to floor, and the future laundry yard was merely a pool of mud, so wet laundry was hung in the unfinished East Room to dry. Thomas Jefferson, the third president, improved the comfort of the White House in many respects and added new architectural features such as the terraces on the east and west ends.   When the British forces burned the White House on August 24, 1814, President Madison was forced to leave.All the remained after the fire was the exterior walls, the interior was completely destroyed. It was not until December of 1817 that the following president, James Monroe, was able to move into a rebuilt residence. Since then, the White House has continued to be modified but has been continuously occupied by each succeeding U.S president.

Question: Approximately how much of the Earth’s atmosphere is nitrogen?