Passage Reference: The sand, rock and boulders that workers excavated were hoisted out of the caisson in huge buckets via a shaft. This was filled with water in order to maintain the correct air pressure.

Common Mistake: Students often write tunnel or pipe because they look similar in a diagram, but those words are not used in the passage. You must copy the exact word. This is a synonym trap.

Paraphrasing: Passage: 'hoisted out of the caisson via a shaft' = Diagram: 'vertical exit for buckets'

Tips: In diagram questions, match the physical shape in the picture with the noun used in the passage.

Key Vocabulary:

• shaft = vertical passage
• hoisted = lifted

Question Focus: Identifying what kept water out of the caisson

Correct Answer: compressed air

Passage Reference: Water was kept out of the chamber at the base of the caisson where the workers dug by means of compressed air, which was pumped in through a special duct in the roof of the caisson.

Why this is correct: The diagram shows what fills the caisson to stop water entering. The passage states water was kept out by means of compressed air, so the correct label is compressed air.

Common Mistake: Some students write air only, but that loses the key detail. The passage is specific. This is a partial truth trap.

Paraphrasing: Passage: 'compressed air was pumped in' = Diagram: 'what keeps water out'

Tips: If the passage uses two words together as one idea, copy both if the word limit allows.

Key Vocabulary:

• compressed = pressurised
• duct = pipe

Question Focus: Identifying the entry system workers passed through

Correct Answer: air lock

Passage Reference: Workers entered via a series of ladders, passing through an air lock on the way down. This had a door on each side, only one of which could be opened at any one time. Had both doors been opened, compressed air would have escaped, with dire consequences for the workers.

Why this is correct: The diagram shows a small enclosed area on the entry route. The passage explains workers entered by passing through an air lock, which matches this part of the diagram.

Common Mistake: Students sometimes write door because the passage mentions doors, but the whole system is called an air lock. This is a context shift trap.

Paraphrasing: Passage: 'passing through an air lock' = Diagram: 'controlled entry area'

Tips: Do not label a small detail if the passage gives a name for the whole system.

Key Vocabulary:

• air lock = pressure control chamber
• consequences = bad results

Question Focus: Identifying where workers actually dug

Correct Answer: chamber

Passage Reference: Water was kept out of the chamber at the base of the caisson where the workers dug by means of compressed air

Why this is correct: The diagram points to the space at the bottom where digging happens. The passage calls this the chamber at the base of the caisson, so the correct label is chamber.

Common Mistake: Some students write base or caisson, but those are broader areas, not the specific workspace. This is a wrong section trap.

Paraphrasing: Passage: 'the chamber at the base of the caisson' = Diagram: 'digging area'

Tips: For location labels, choose the most precise noun, not a general one.

Key Vocabulary:

• chamber = enclosed space
• base = bottom

General Tips:

• Diagram completion answers come directly from the passage. Never invent your own word.
• Follow passage order. The first label appears earlier in the text than the last.
• Check the word limit carefully. Extra words make the answer wrong.
• Match the diagram shape to the description in the passage before choosing the word.