Step 1: Flame of the forest unmistakably refers to Butea monosperma.
Step 2: Only one of the four options places this pair together.
Step 3: The remaining pairs (Bauhinia purpurea, Callistemon lanceolatus, Lagerstroemia flos-reginae) match the same option's other entries.
Step 4: The correct answer is (A)-(II), (B)-(I), (C)-(IV), (D)-(III).