Select all sentences in which the verb form correctly expresses duration, result or recent evidence.
The volunteers have prepared twenty food parcels, and all twenty are ready.✓Respuesta correcta
I have polished the long corridor for three hours and am still only halfway along it.
The floor is dusty because the builders have been sanding the doors.✓Respuesta correcta
The assistant has been processing exactly nine applications, and all nine are complete.
Explicación
The food-parcel sentence correctly uses the simple perfect for a completed total, and the dusty-floor sentence correctly uses the continuous for visible evidence of recent activity. The corridor needs the continuous because the work is unfinished, while the applications sentence wrongly pairs the continuous with an exact completed total.