Which SQL statements are valid?

See the Exhibit and examine the structure of the PROMOSTIONS table:

Which SQL statements are valid? (Choose all that apply.)

A.
SELECT promo_id, DECODE(NVL(promo_cost,0), promo_cost,
promo_cost * 0.25, 100) “Discount”
FROM promotions;
—B. SELECT promo_id, DECODE(promo_cost, 10000,
DECODE(promo_category, ‘G1’, promo_cost *.25, NULL),
NULL) “Catcost”
FROM promotions;

C.
SELECT promo_id, DECODE(NULLIF(promo_cost, 10000),
NULL, promo_cost*.25, ‘N/A’) “Catcost”
FROM promotions;

D.
SELECT promo_id, DECODE(promo_cost, >10000, ‘High’,
<10000, ‘Low’) “Range”
FROM promotions;

Explanation:
The DECODE Function
Although its name sounds mysterious, this function is straightforward. The DECODE function
implements ifthen-else conditional logic by testing its first two terms for equality and returns the
third if they are equal and optionally returns another term if they are not.
The DECODE function takes at least three mandatory parameters, but can take many more. The
syntax of the function is DECODE(expr1,comp1, iftrue1,
[comp2,iftrue2…[ compN,iftrueN]], [iffalse]).