Get the column name which is a primary key

Sql server

DECLARE @TableName VARCHAR(128)
SELECT @TableName = 'test_table'

SELECT c.COLUMN_NAME 
FROM
    INFORMATION_SCHEMA.TABLE_CONSTRAINTS pk ,
    INFORMATION_SCHEMA.KEY_COLUMN_USAGE c
WHERE
    pk.TABLE_NAME = @TableName
    AND CONSTRAINT_TYPE = 'PRIMARY KEY'
    AND c.TABLE_NAME = pk.TABLE_NAME
    AND c.CONSTRAINT_NAME = pk.CONSTRAINT_NAME