Concept:Tactic movement (taxis) is the directed locomotion of a motile organism in response to an external stimulus.
Explanation:Euglena is a motile, unicellular organism that swims using its flagellum.
When light is present from one side, Euglena changes its swimming direction and moves towards the light source.
This directed, whole-body movement towards light is called phototaxis.
Phototaxis is a type of tactic movement because it involves actual locomotion directed by the stimulus.
Tropic movements are growth responses, usually seen in plants, not free locomotion.
Nastic movements are non-directional responses of plant parts to a stimulus.
Kinetic movements are random or undirected movements whose speed changes with stimulus intensity.
Since Euglena moves its entire body purposefully towards light, the behaviour matches tactic movement only.
Answer:B. tactic movement