Multiple choice softskills communication They have built a perfect dam across the river. Across the river a perfect dam was built. A perfect dam has been built by them across the river. A perfect dam should have been built by them. Across the river was a perfect dam. Reveal answer Fill a bubble to check yourself B Correct answer Explanation The active sentence is in the present perfect tense ("have built"). Its passive equivalent must use "has/have been built". This makes "A perfect dam has been built by them across the river" the correct choice.