To determine the most likely definition of the root "flu," we need to examine the given words and their definitions carefully.
1. Influx: The movement into an area.
- Key aspect: Movement into a specific place, which indicates some form of flow or movement.
2. Effluent: Wastewater discharged into the environment.
- Key aspect: Discharged, suggesting flow outwards into the environment.
3. Reflux: To return or flow back into something.
- Key aspect: Flowing back, again indicating movement or flow.
4. Fluid: Capable of flowing or moving freely like water.
- Key aspect: Flowing or moving freely, indicative of the nature of flow.
By analyzing these words:
- All definitions refer to some form of movement or flow.
- The terms "movement into," "discharged into" (hints at movement out), "flow back" (reverse movement), and "flowing freely" all consistently signal flow or movement.
Given the consistent theme of movement and flow across all definitions, the most likely definition of the root "flu" must be "flow."
Thus, the correct answer is:
flow
