Identify the single incorrect statement about common hydraulic concepts:

Introduction / Context:
This item checks conceptual clarity on energy composition, venturimeter geometry, Pitot tube use, and the meaning of two-dimensional flow. Only one statement is intentionally incorrect.

Given Data / Assumptions:

• Inviscid-energy picture for Bernoulli's components (pressure, velocity head, elevation).
• Standard venturimeter with smooth convergent and longer diffuser.
• Pitot tube measures stagnation and static pressure for local velocity.
• Two-dimensional flow refers to dependence on two spatial coordinates.

Concept / Approach:
Two-dimensional (2D) flow is defined by velocity components u(x,y,t), v(x,y,t) with no variation in the third coordinate. Streamlines may be curved or straight in 2D; curvature does not make the flow 3D. Venturimeters use a longer diffuser to limit adverse pressure gradients and suppress separation.

Step-by-Step Solution:

Verification / Alternative check:
Classic 2D potential flows (e.g., around a cylinder) have strongly curved streamlines yet remain 2D (no spanwise variation).

Why Other Options Are Wrong:

• (a), (b), (c) are standard and widely taught facts.
• (e) claims all are correct, which is false because (d) is incorrect.

Common Pitfalls:
Equating streamline curvature with three-dimensionality; assuming equal convergent and divergent lengths in a venturimeter.

Final Answer:
Two-dimensional flow means streamlines are necessarily straight lines; curved streamlines cannot be two-dimensional.