Which of the following statements is valid? (refer to the tables in the JustLee Books database.) a. SELECT title FROM books WHERE retail

Which of the following statements is valid? (refer to the tables in the JustLee Books database.)
a. SELECT title FROM books
WHERE retail<(select cost="" from="">
WHERE isbn = '9959789321');
b. SELECT title FROM books
WHERE retail = (SELECT cost FROM books
WHERE isbn = '9959789321' ORDER BY cost);
c. SELECT title FROM books
WHERE category IN (SELECT cost FROM orderitems
WHERE isbn = '9959789321');
d. none of the above statements