The correct answer is 'Idled' Key Points Drudged(verb): do hard menial work. example: I drudged through the day cleaning in my new apartment. Idled(verb): not turned to normal or appropriate use, inactive. example: I sat idle at home during the weekend. Hence, the word drudged should be replaced with idled to form a contextually correct sentence. The correct option is option 3. It should read as: Nearly 30% of Russia's refining capacity was idled in May, sources told Reuters. Additional Information Let us understand the meaning of other words Grubbed(verb): search in a clumsy and unmethodical manner. example: She grubbed through her room looking for her college documents. Plowed(verb): to proceed steadily and laboriously. example: He plowed through the work and was paid his wage at the end of the day. Slaved(verb): to work very hard. example: I slaved through the weekend for my exam on monday. Exerted(verb): to make use of something, for example influence, strength, etc., to affect somebody/something. example: He exerted his full power to stop the goons from attacking the lady.