Select the most appropriate tone of the passage.

Concept: The tone of a passage is the writer's attitude towards the subject, inferred from word choice and from the purpose the writing serves. Writing that sets out to define a subject, explain how it works and list its causes — in plain, verifiable, unemotional vocabulary, with no attempt to persuade, entertain or reminisce — carries an informative tone. Naming a tone therefore means matching the writer's stance to the tone word whose definition fits it, not reporting how the reading felt.

Application: This passage does exactly that. It defines cataract as a major cause of blindness, explains the mechanism by which it develops — the lens of the eye hardens, loses its transparency, becomes opaque and obstructs light rays from entering the eye — and then states the effects, namely blurred vision and sometimes multiple images in place of a single object image. It goes on to list the contributing factors: old age, a hereditary defect present at birth, eye injuries, long exposure to sunrays, the smoke inhaled while smoking, and ultraviolet radiation. Every sentence supplies a fact or an explanation; none argues a position, invents an incident or dwells on a personal feeling.

Cross-check — how the other tone words differ:

• Fictitious means invented or imaginary; it would require made-up incidents or characters, whereas each statement here is offered as a verifiable medical fact.

• Boring names a reader's reaction of tedium rather than the writer's attitude, so it describes the audience's experience instead of the stance the text takes.

• Pensive means deeply, often wistfully reflective; it would require unhurried personal musing, which this factual account does not contain.

The writer's stance throughout is that of someone supplying facts and explanation, so the most appropriate tone of the passage is informative.