a)

SELECT model, speed, hd
FROM PC
WHERE price < 1200;

b)

SELECT model, speed AS megahertz, hd AS gigabytes
FROM PC
WHERE price < 1200;

c)

SELECT DISTINCT maker
FROM Product
WHERE type = "printer";

d)

SELECT model, ram, screen
FROM Laptop
WHERE price > 2000;

e)

SELECT *
FROM Printer
WHERE color;

f)

SELECT model, speed, hd
FROM PC
WHERE (rd = "12xDVD" OR rd = "16xDVD") AND price < 2000;