Concept:In passive voice, the object of the active sentence becomes the subject. The verb changes to a form of 'be' + past participle. Both clauses must be converted.
Explanation:The active sentence has two parts: "The company has recruited four hundred engineers" and "who will have to complete an internship for three weeks."
Convert the first part: Object "four hundred engineers" becomes subject. Change "has recruited" to "have been recruited by the company".
Convert the second part: The relative clause "who will have to complete an internship" becomes "an internship of three weeks will have to be completed by them".
Combine both parts with "and" to keep the meaning intact.
Option B leaves the second clause in active voice. Option C reverses subject and object, changing meaning. Option D uses wrong tense ("will have had to be completed").
Only Option A correctly converts both clauses into passive voice without errors.
Answer:Option A: "Four hundred engineers have been recruited by the company and an internship of three weeks will have to be completed by them."