ANS:A - x

For flow past a flat plate, in the context of boundary layer theory, the boundary layer thickness δ\deltaδ is proportional to the square root of the distance xxx along the plate in the direction of flow. Mathematically, this relationship is expressed as: δ∝x\delta \propto \sqrt{x}δ∝x​ This indicates that as the distance xxx increases along the plate, the boundary layer thickness δ\deltaδ increases, but not linearly. Instead, it increases in proportion to the square root of xxx. Therefore, the correct relationship is: δ∝x\delta \propto \sqrt{x}δ∝x​ This corresponds to the option where boundary layer thickness is proportional to 1/x1/\sqrt{x}1/x​.