\[\overleftrightarrow{OQ}\bot \overleftrightarrow{PR}\] What is the measure of \[\angle QOR\]?

• A.  \[{{180}^{o}}\]                  
• B.         \[{{45}^{o}}\]
• C.  \[{{90}^{o}}\]                     
• D.         \[{{120}^{o}}\]