B - Incorrect: Were unsanitary and ranging are not parallel. The relative pronoun "that" is missing.
C - Incorrect: The construction obscures the meaning, which should be that the survey did not find unsanitary conditions in the other 10% -- not that it did not find a range of unsanitary conditions.
E - Incorrect: This option is awkward and wordy. The separation by a semicolon also obscures the connection between unsanitary conditions and range.
D - Correct: This choice makes it clear that 90% had unsanitary conditions which are then described.
This gives a whole new meaning to the “South Beach Diet.”