Over the past several years, the owner of a boutique on Aspen Avenue has observed a pattern in the amount of revenue for the store. The revenue reaches a maximum of about $47000 in January and a minimum of about $28000 in July. What kind of function best represents this pattern of revenue over time?
A) Linear function
B) Quadratic function
C) Exponential function
D) Sine function
E) Logarithmic function