Which of the following queries demonstrates the correct way to compare a tuple to a row subquery?

The table Country contains the fields Code, defined as the PRIMARY KEY, and Name, which is covered by a UNIQUE index.

Which of the following queries demonstrates the correct way to compare a tuple to a row subquery?

A.
SELECT Name
FROM City c
WHERE (c.id, c.CountryCode) = (SELECT
CONCAT(Capital, Code)
FROM Country
WHERE Name = ‘United States’)

B.
SELECT Name
FROM City c
WHERE (c.id, c.CountryCode) = (SELECT Capital
FROM Country,
SELECT Code
FROM Country)

C.
SELECT Name
FROM City c
WHERE (c.id, c.CountryCode) = (SELECT Capital, Code
FROM Country)

D.
SELECT Name
FROM City
WHERE (c.id, c.CountryCode) = (SELECT Capital, Code
FROM Country
WHERE Name = ‘United States’)

Explanation:
tuple = list of ordered elements, eg list (c.id, c.CountryCode). A only returns 1 value, B is incorrect syntax, C multiple rows (no WHERE).