We were all afraid when the alarm … .

Analyze the question: The sentence is "We were all afraid when the alarm ____." We need the phrasal verb that correctly describes an alarm suddenly sounding.

Explain the concept: This question tests phrasal verbs (a verb plus a particle like off, up, out). The meaning of a phrasal verb is often different from the meanings of its separate words, so you have to know the idiom.

• go off = (of an alarm, bell, or siren) to start ringing or sounding. Example: The fire alarm went off at midnight.

Check each option:

• A. died off: means to die one after another, or to disappear gradually (e.g., "The old trees died off"). It doesn't describe an alarm sounding, so it doesn't fit.
• B. went off: means the alarm began to sound. This makes sense, since a sudden alarm would make people afraid. ✔
• C. ran off: means to flee or to run away (e.g., "The thief ran off"). An alarm doesn't run away, so this is wrong.
• D. rang up: means to telephone someone (e.g., "She rang me up"). It is not used for an alarm sounding, so this is wrong.

Answer: The sentence reads correctly as: *We were all afraid when the alarm went off.

Tip: Learn common "go off" uses for exams:

• An alarm / bell / bomb goes off (sounds or explodes).
• Food goes off (spoils).
• A light or power goes off (switches off).

Whenever you see "alarm" in a sentence, think of "go off."