Who had done the work? The correct passive voice of this sentence is :
By whom the work had done?
By whom had the work done?
By whom had the work been done?
Who the work had been done?
Explanation:
Correct Answer is: By whom had the work been done?

By whom the work had done?
By whom had the work done?
By whom had the work been done?
Who the work had been done?
Correct Answer is: By whom had the work been done?

What is the `noun` form of the word `beneficial`? Option A: benificialness , Option B: benefit , Option C: beneficient, Option D: beneficiary, correct answer is: benefit
What is the noun form of the word `know`? Option A: knowing , Option B: knowledge , Option C: knowledgeable, Option D: known, correct answer is: knowledge
You should dress for cold weather today. Here the underlined word is a : Option A: Conjunction , Option B: Preposition , Option C: verb, Option D: noun, correct answer is: verb
`Forgiveness in a great virtue`.Which class of noun `forgiveness`` belongs to? Option A: Collective , Option B: Common , Option C: Material, Option D: Abstract, correct answer is: Abstract
Human brain is the most sophisticated machine. Here `sophisticated` is a/an___. Option A: noun , Option B: verb , Option C: adjective, Option D: adverb, correct answer is: adjective