Which one of the following is satisfied if the flow is irrotational for a two-dimensional fluid element in the \[x-y\] plane?

• A. \[\frac{\partial v}{\partial x}=\frac{\partial u}{\partial y}\]                        
• B. \[\frac{\partial v}{\partial x}=\frac{\partial u}{\partial y}\]
• C. \[\frac{\partial u}{\partial x}=\frac{\partial v}{\partial y}\]                        
• D. \[\frac{\partial u}{\partial x}=\frac{\partial v}{\partial y}\]