How can you modify the subquery to return a single value?

The correct answer is B) Add a TOP 1 clause to the subquery.

To modify a subquery to return a single value, you can use the TOP 1 clause in the subquery to limit the result set to a single row. This will ensure that the subquery returns only one value, which can then be used in the outer query.

For example, consider the following query:

SELECT name FROM customers WHERE customer_id = (SELECT customer_id FROM orders WHERE order_total > 1000)

If the subquery returns multiple customer_id values, the error “Subquery returned more than 1 value” will be thrown. To fix this, you can modify the subquery as follows:

SELECT name FROM customers WHERE customer_id = (SELECT TOP 1 customer_id FROM orders WHERE order_total > 1000)