Select the verb to fill in the blank in the following sentence:- It w…

The correct answer is Option (3) → taught

Active	Passive
Someone had taught them how it worked.	They had been taught how it worked.

Passive voice in the past perfect:

• Object becomes subject: "them" in the active sentence becomes "they".
• Tense kept: be + past participle, in the same tense:
  • past perfect "had taught" → "had been taught", so the blank needs a past participle.
• Agent (by ...): "by someone" is left out because it does not matter who taught them.
• The verb must take a person as its object: we teach someone how something works, so "they" can become the subject. Taught is the only option that does this.
• Complete sentence: It wasn't the first time they had been taught how it worked.
  Example: We were taught how to swim in the summer camp.

Why the Other Options are Incorrect?

Option 1: reported — Incorrect.

• To report is to give an account of something.
• One reports a fact to a person, so "they had been reported how it worked" is ungrammatical.
  Example: The guard reported the theft to the police.

Option 2: exclaimed — Incorrect.

• To exclaim is to cry out suddenly in surprise or anger.
• It does not take a person as object, so it cannot be made passive this way.
  Example: "What a lovely view!" she exclaimed.

Option 4: inferred — Incorrect.

• To infer is to work out a conclusion from evidence.
• One infers a fact, not a person, so "they had been inferred" makes no sense.
  Example: From his silence I inferred that he was upset.

Contrast: we teach a person how something works, so the person can be the passive subject; "report", "exclaim" and "infer" do not take a person as object in this way.