Which part of the graph is represented by B$?$

The image shows the stages of the business cycle. On the vertical axis is real GDP measured in trillions. On the horizontal axis is the year, ranging from $2004$ to $2018.$ There is a single curve that shows the GDP measurements for the United States. From $2004$ to $2008$ it is increasing from left to right. The end of the increase is labeled A$.$ The decline, from $2008$ to $2010,$ is labeled C$,$ and ends at the point labeled B$.$ Then, from $2010$ to $2018,$ the curve increases and is labeled D$.$

expansion

trough

recession