In Omaha it is very important to be able to recognise what the best possible ('nut') hand is for any given board. Each player has four cards rather than two, so it is much more likely that someone will actually be holding a nut hand in Omaha than it is in Hold'em.
Although there is an Ace-high straight among the board cards, in Omaha this does not necessarily mean that you have that straight yourself. Hand A can make the nut straight using the Jack and Ten from his hand: A-K-Q-J-10. The best that Hand B can do is a Queen-high straight: Q-J-10-9-8.
If there is a straight in the five board cards in Hold'em then everyone can use this as their minimum best hand. However, in Omaha this is not the case. You still must use two of your hole cards.
Here Hand A has an Ace-high flush with a Queen kicker: A-Q-J-10-9. He does not have a straight flush because he can only use two of his hole cards. In fact, Hand B wins this hand with the nut Ace-high flush, King kicker: A-K-10-9-2.