Analyze the graph below and answer the question that follows.
A line graph of population gap between the U S and Japan. The x-axis is labeled from 1950 to 2010. The y-axis is labeled Population in millions from 0 to 350. Japan is the bottom line and the U S is the top line. In 1950, the U S is about 150 million and Japan is almost 100 million. In 1970, the U S is at 200 million and Japan is at 100 million. In 1980, the U S is over 200 million and Japan is around 125 million. In 2010, the U S is over 300 million and Japan is almost 150 million.
Data courtesy of the UN Population Division 2010

According to the graph above, the population gap between the United States and Japan is __________.
A.
widening
B.
shrinking
C.
unchanging
D.
undetermined