The relation that must hold for the flow to be irrotational is

• A. <img src="/_files/images/civil-engineering/gate-exam-questions/911-267-1.png">
• B. <img src="/_files/images/civil-engineering/gate-exam-questions/911-267-2.png">
• C. <img src="/_files/images/civil-engineering/gate-exam-questions/911-267-3.png">
• D. <img src="/_files/images/civil-engineering/gate-exam-questions/911-267-4.png">