The question requires dropping rows where all columns have missing values. The correct method to achieve this is by using na.drop("all"), which checks for rows with nulls in all columns. Option A and B are incorrect because they use the default behavior which drops rows with any null values, not necessarily all. Option C is incorrect because it specifies a subset column 'sqft', which means it only checks for nulls in that specific column, not all columns. Option D is correct as it uses na.drop("all") without a subset, thus checking all columns for null values. Option E is incorrect due to a syntax error in the method name (nadrop instead of na.drop).