Answer:
Pathline
Step-by-step explanation:
- The smoke coming out of the chimney on a day with variable winds would most closely relate to a path-line. Consider a smoke particle " grey " color particle that is injected into air at every instant in time and follows a continuous "path" along the flow of the of the fluid.
- A streakline concentrates on fluid particles that have gone through a fixed station or point. At some instant of time the position of all these particles are marked and a line is drawn through them.
- The streakline and pathline can coincide on the conditions of flow to be steady that is the rate of change of flow of the air is continuous and does not change with time in a day i.e the variation in the winds or any discontinuity is removed.