A study was done to investigate the population of polar bears over time. The correlating linear model is shown below, where x represents the number of years after 1955, and y represents the number of polar bears. Interpret the y-intercept.
y = 5,000 + 500x

A. There were 10,000 polar bears in 1955.
B. There were 1,000 polar bears in 1955.
C. There were 5,000 polar bears in 1955.
D. There were 500 polar bears in 1955.