Select the option that expresses the given sentence in passive voice. Scientists were conducting experiments on the newly discovered species.

Correct — B. The active verb is were conducting — past continuous — and the past continuous passive is built as was/were + being + past participle.

Next, which noun moves. The object of 'conducting' is experiments; 'on the newly discovered species' is a prepositional phrase hanging off it, so it travels with the noun and is not promoted.

That gives: Experiments + were being conducted + on the newly discovered species + by scientists.

Only option (b) keeps the tense and takes the right noun as subject.

Why the others are wrong

• (a)
  The newly discovered species has been conducting experiments by scientists. — Has been conducting is still active — it makes the species the one doing the experimenting — and it is present perfect continuous, not past continuous. A by-phrase cannot turn an active verb passive.
• (c)
  The newly discovered species has been experimented on by scientists. — Has been experimented on is present perfect, so the tense has changed, and it promotes the species, which is only the object of a preposition, to subject.
• (d)
  Experiments on the newly discovered species had been conducted by the scientists. — The subject is right, but had been conducted is past perfect. Past continuous needs 'were being conducted'; 'had been' pushes the action into a completed earlier past.

Changing voice keeps the tense and changes only the arrangement. Every active tense has one passive shape, and past continuous maps to was/were + being + V3.

The second rule decides which noun becomes the subject. Only the direct object of the active verb can move; a noun sitting inside a prepositional phrase stays where it is.

'Conduct' takes 'experiments' as its object here, so 'experiments' becomes the subject and 'on the newly discovered species' stays attached to it.

Key facts

• Past continuous passive is was/were + being + past participle.
• Present continuous passive is is/am/are + being + past participle.
• A noun sitting inside a prepositional phrase cannot become the passive subject, because only the direct object of the active verb moves.

Common traps

• Promoting the noun after a preposition instead of the verb's real object.
• Shifting to a perfect tense because it reads more smoothly than the continuous.
• Accepting an option because it ends in a by-phrase, even though its verb is still active.

No directly related past PYQ was found.