Uniform flow occurs when A. the flow is steady B. the flow is streamline C. size and shape of the cross section in a particular length remain constant D. size and cross section change uniformly along length

The correct answer is: C. size and shape of the cross section in a particular length remain constant.

A uniform flow is a flow in which the velocity of the fluid is the same at all points in a given cross section and at all times. This means that the size and shape of the cross section in a particular length remain constant.

A steady flow is a flow in which the velocity of the fluid at a given point does not change with time. This does not mean that the velocity of the fluid is the same at all points in the flow.

A streamline flow is a flow in which the fluid particles move in smooth, parallel lines. This does not mean that the flow is uniform.

A non-uniform flow is a flow in which the velocity of the fluid is not the same at all points in a given cross section or at all times. This means that the size and shape of the cross section in a particular length change.