Passage Reference: A vertical flow (downflow) reed bed is a sealed, gravel filled trench with reeds growing in it.

Common Mistake: Some students choose reed beds because they see the word "reed" in the passage. But the diagram label points to the plant itself, not the whole system. This is a context shift trap.

Paraphrasing: Passage: 'reeds growing in it' = Diagram: 'plant at the top'

Tips: Check carefully whether the label points to a thing, a layer, or the whole system.

Key Vocabulary:

• reed = wetland plant
• trench = long narrow hole

Question Focus: The diagram shows the first layer the wastewater flows through below the surface.

Correct Answer: E

Passage Reference: In vertical flow reed beds, the wastewater is applied to the top of the reed bed, flows down through a rhizome zone with sludge as a substrate,

Why this is correct: The diagram label is for the material in the rhizome zone. The passage tells us this zone has sludge as a substrate, so the answer is sludge.

Common Mistake: Many students choose sand because sand is also mentioned soon after. But sand belongs to the next layer, not this one. This is a wrong section trap.

Paraphrasing: Passage: 'sludge as a substrate' = Diagram: 'material in this layer'

Tips: Follow the flow direction step by step. Each layer matches the passage order.

Key Vocabulary:

• sludge = thick waste material
• substrate = base material

Question Focus: The diagram points to the layer below the sludge zone.

Correct Answer: F

Passage Reference: flows down through a rhizome zone with sludge as a substrate, then through a root zone with sand as a substrate,

Why this is correct: After the sludge layer, the passage says the water moves through a root zone with sand as a substrate. This matches the diagram position, so the answer is sand.

Common Mistake: Some students pick gravel because it is also a drainage material. But gravel comes later, after the sand. This is a sequence trap.

Paraphrasing: Passage: 'sand as a substrate' = Diagram: 'material in this middle layer'

Tips: When labeling layers, always check what comes before and after in the passage.

Key Vocabulary:

• root zone = area around roots
• flows down = moves downward

Question Focus: The diagram shows the drainage layer near the bottom of the system.

Correct Answer: B

Passage Reference: followed by a layer of gravel for drainage,

Why this is correct: The passage clearly says there is a layer of gravel for drainage before the final collection system. This matches the diagram label, so the answer is gravel.

Common Mistake: Students sometimes choose large stones here. But large stones are part of the under drainage system below the gravel. This is a partial truth trap.

Paraphrasing: Passage: 'layer of gravel for drainage' = Diagram: 'drainage layer'

Tips: Look for purpose words like "for drainage" to match the correct layer.

Key Vocabulary:

• gravel = small stones
• drainage = removal of water

Question Focus: The diagram labels the depth of the vertical reed bed.

Correct Answer: G

Passage Reference: The reeds in a downflow system are planted in a bed 60cm deep.

Why this is correct: The diagram asks for the depth measurement. The passage states the reeds are planted in a bed 60cm deep, so the correct label is 60cm.

Common Mistake: Some students choose 100m because they remember a number from earlier. But 100m refers to the length of a horizontal reed bed, not this system. This is a wrong section trap.

Paraphrasing: Passage: '60cm deep' = Diagram: 'depth of the bed'

Tips: Be careful with numbers. Always check which system the measurement belongs to.

Key Vocabulary:

• deep = how far down
• planted = put into the ground

General Tips:

• Diagram labels usually follow the passage order. Read from top to bottom.
• Pay close attention to layers and sequence words like first, then, followed by.
• Numbers are common traps. Check what each measurement describes.
• If two options seem similar, re-read the exact sentence in the passage.