Epidemiologists Tried to Investigate the Role of Factor Y in the Exposure-Disease

Epidemiologists tried to investigate the role of factor Y in the exposure-disease relationship.They developed three tables to show the exposure-disease relationship based on the status of factor Y.In this analysis,what is the odds ratio in the overall population? $\text { Overall }$
$\begin{array}{|l|l|l|}\hline & \text { Case } & \text { Control } \\\hline \text { Exposed } & 1,000 & 500 \\\hline \text { Unexposed } & 200 & 500\\\hline\end{array}$

$\text { Factor } Y \text { present }$
$\begin{array}{|l|l|l|}\hline & \text { Case } & \text { Control } \\\hline \text { Exposed } & 800 & 250 \\\hline \text { Unexposed } & 100 & 250 \\\hline\end{array}$

$\text { Factor } Y \text { absent }$
$\begin{array}{|l|l|l|}\hline & \text { Case } & \text { Control } \\\hline \text { Exposed } & 200 & 250 \\\hline \text { Unexposed } & 100 & 250 \\\hline\end{array}$

A) 0.5
B) 1.0
C) 2.0
D) 5.0
E) 8.0