Select the correct passive construction: 'Researchers have demonstrated the efficacy of the new solar desalination membrane.'
Answer and explanation
Correct answer: D. The efficacy of the new solar desalination membrane has been demonstrated by researchers.
- Step 1: Identify active verb tense: 'have demonstrated' is present perfect active.
- Step 2: Form present perfect passive: 'has/have + been + past participle'.
- Step 3: Determine subject number: 'The efficacy' is singular, requiring 'has been demonstrated'.
Answer
The efficacy of the new solar desalination membrane has been demonstrated by researchers.
Why not the others: 'is demonstrated' is simple present passive; 'was demonstrated' is simple past passive; 'had been demonstrated' is past perfect passive.
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