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d) Considering the following CREATE TABLE statement, why when the 'region' column is part of the primary key's underlying clustered index, do the query optimizers resort to a table scan when a WHERE clause contains only conditions on the 'region' column? CREATE TABLE sales year SMALLINT NOT NULL, quarter' TINYINT NOT NULL, region VARCHAR(50) NOT NULL, vehicle VARCHAR(50) NOT NULL, quantity SMALLINT NULL, CONSTRAINT pri_sales PRIMARY KEY (year', quarter, region, vehicle)); [3] ] e) Continuing with the preceding scenario, suggest a new non-clustered index to stop the query optimizers having to resort to a table scan [3]