Create a SQL query which shows the most active seller (the one who has offered the most number of items) along with the number of items offered by that seller given the following tables:

Table 1: SELLER

	SELLER_ID	SELLER_NAME	USERNAME	PASSWORD
1	1	ADAM	A123	A
2	2	BOB	B456	B
3	3	CHARLIE	C789	C

TABLE 2: ITEM

	ITEM_ID	NAME	INITIAL_PRICE	DESCRIPTION	QUANTITY
1	1	LAPTOP COMPUTER	300.00	2015 HP LAPTOP	1
2	2	RUBBER BALL	7.00	BOUNCY	20
3	3	TOY	30.00	STUFFED ANIMAL	1
4	4	HOCKEY STICK	55.00	WOOD	5

TABLE 3: OWNER

	SELLER_ID	ITEM_ID
1	1	1
2	2	2
3	3	3
4	2	4