No. 10
Question :
Many theories on conserving the purity of water has been proposed, but not one has been as widely accepted as this one
Answer :
Many theories on conserving the purity of water have been proposed, but not one has been as widely accepted as this one.
(reason 1: karena "has been" bukan sungular, maka diperbaiki menjadi "have been")
(reason2: karena "have been" ditujukan untuk sebuah benda)
