Passage Reference: Perturbations of nebulous interstellar clouds in space result in gravitational interaction, with the consequent contraction of gaseous matter to create protostars, which are much larger than the stars they will finally become.

Common Mistake: Students may write stars, but the passage clearly says protostars, which are earlier and larger. This is a partial truth trap.

Paraphrasing: Passage: 'create protostars' = Diagram: 'formation of early stars'

Tips: Use the diagram order and match each stage to the passage step by step.

Key Vocabulary:

• nebulae = clouds of gas
• contraction = becoming smaller

Question Focus: Synonym match - gas changes state

Correct Answer: plasma

Passage Reference: As the temperature increases, the gas becomes completely ionised to form plasma and gravitational contraction of the core then takes place.

Why this is correct: The diagram shows what the gas becomes when temperature rises. The passage states the gas becomes completely ionised to form plasma.

Common Mistake: Students may write ionised gas, but you must copy the exact word from the passage. This is a synonym trap.

Paraphrasing: Passage: 'becomes completely ionised to form plasma' = Diagram: 'gas changes into ___'

Tips: For FIB, always copy the exact word used in the passage.

Key Vocabulary:

• ionised = electrically charged
• plasma = hot charged gas

Question Focus: Process identification - energy production

Correct Answer: nuclear fusion

Passage Reference: The onset of hydrogen-burning happens at a core temperature of several million degrees, and converts hydrogen to helium through nuclear fusion.

Why this is correct: The diagram asks how hydrogen is converted to helium. The passage clearly says this happens through nuclear fusion.

Common Mistake: Writing fusion alone loses important meaning. This is a partial truth trap.

Paraphrasing: Passage: 'converts hydrogen to helium through nuclear fusion' = Diagram: 'process that converts hydrogen'

Tips: If the passage gives a full term, copy the full term, not a shortened version.

Key Vocabulary:

• fusion = joining together
• hydrogen-burning = using hydrogen as fuel

Question Focus: Stage name - longest period

Correct Answer: main sequence

Passage Reference: The greater part of a star's evolutionary lifetime is spent hydrogen-burning and, during this period, it is said to be on the Main Sequence.

Why this is correct: The diagram labels the long stable period of a star's life. The passage says during hydrogen-burning it is on the Main Sequence.

Common Mistake: Students may write sequence only, which is incomplete. This is a partial truth trap.

Paraphrasing: Passage: 'spent hydrogen-burning ... on the Main Sequence' = Diagram: 'long stable stage'

Tips: Check capitalised terms in the passage. They are often exact answers.

Key Vocabulary:

• evolutionary lifetime = life stages
• sequence = ordered stages

Question Focus: Product of hydrogen-burning

Correct Answer: helium

Passage Reference: The onset of hydrogen-burning happens at a core temperature of several million degrees, and converts hydrogen to helium through nuclear fusion.

Why this is correct: The diagram asks what hydrogen becomes. The passage states it converts hydrogen to helium.

Common Mistake: Students may write energy, but energy is released, not the product. This is a context shift trap.

Paraphrasing: Passage: 'converts hydrogen to helium' = Diagram: 'new element formed'

Tips: Look for 'to' phrases in the passage. They often show results.

Key Vocabulary:

• convert = change into
• element = basic substance

Question Focus: Later evolutionary stage

Correct Answer: a red giant

Passage Reference: The end of hydrogen-burning is marked by the evolution of a star into a red giant, when it is said to leave the Main Sequence.

Why this is correct: The diagram shows what the star becomes after hydrogen-burning ends. The passage says it evolves into a red giant.

Common Mistake: Writing giant alone is too vague. This is a partial truth trap.

Paraphrasing: Passage: 'evolution of a star into a red giant' = Diagram: 'star becomes ___'

Tips: Articles like 'a' are sometimes optional if the diagram does not show them.

Key Vocabulary:

• evolve = change over time
• giant = very large star

Question Focus: Purpose of contraction

Correct Answer: maintain equilibrium

Passage Reference: Burning ceases completely in the core, which undergoes gravitational contraction to maintain mechanical equilibrium.

Why this is correct: The diagram asks why contraction continues at the final stage. The passage explains it is to maintain mechanical equilibrium.

Common Mistake: Students may write equilibrium only, but the verb is needed to explain purpose. This is a grammar trap.

Paraphrasing: Passage: 'to maintain mechanical equilibrium' = Diagram: 'reason for contraction'

Tips: If the diagram asks 'why', look for 'to + verb' phrases in the passage.

Key Vocabulary:

• maintain = keep
• equilibrium = balance

General Tips:

• Diagram completion answers follow passage order. Find the first stage, then move forward.
• Always copy the exact word or phrase from the passage. Do not invent synonyms.
• Check the word limit carefully. Even one extra word is wrong.
• Use grammar clues in the diagram. Look for nouns after articles and verbs after 'to'.