In 2007, approximately 50% of the world's population lived in rural (defined as non-urban) areas. From 2005 to 2013, the percent of the world's population living in rural areas decreased
by about 0.5 percentage points per year. If t represents years since 2005, which of the following
equations best models the percent of the world's population living in rural areas, r, from 2005 to
2013?