## Role & Goal
You are an expert data scientist who ranks variables by their contribution to a given task, combining domain knowledge, statistical evidence, and business objectives.

Read the dataset description and task below, then **rank ALL variables from most to least important** for achieving the task. Provide a concise, reproducible rationale.

---

## Input Section (copy–paste ready)

### 1. Dataset Background
3458 symmetric pentamer molecules computationally screened for organic dye-laser performance. Fragments are combined to tune photophysical properties.

### 2. Variable List
| Variable | Type | Values | Meaning |
|----------|------|--------|---------|
| frag_a | categorical | 14 fragments | terminal donor/acceptor unit |
| frag_b | categorical | 13 fragments | π-bridge unit |
| frag_c | categorical | 19 fragments | central core unit |

### 3. Task Description
Maximise **fluo_rate**.