chess opening for black explained

As for study time, I think it would depend upon which lines you select in a focused repertoire. If you mean to learn the entire opening complexes, I would guess the KID would take the most time, with a large amount of theory and more complicated lines, then probably about on a par would be the QG (since it also encompasses a wide range of variations), and then the QID. Since you're apparently already prepared for 1 d4 Nf6 2 c4 e6 3 Nc3, I think the Bogo is the simplest to learn against 3 Nf3. Barring that, my guess would be it's a toss up between learning some lines of the QID after 3 ... b6 or transposing to the QGD with 3 ... d5 and selecting a specific defense.

One caveat if you decide to go with the QGD with 3 ... d5 is that you'll also need to be prepared against the Catalan if White elects 4 g3.

However, the Catalan might not be a problem, since with subsequent moves ... c6 and ... dxc4, I would guess that might still transpose into Slav lines.

It looks like IronIC_U had a pretty good idea with the Slav.

I have read this book cover to cover, and I am in the process of forgetting it. It isn't worth much. It assumes that you are okay with a draw, and I am most certainly not. I always go for the win, no matter my opponent's rating, color, etc. I play the Dutch against d4 and have decent success. Most importantly, I believe using my own brain during the opening is crucial. My coach said, "Openings don't really matter. Spend your time doing learning endgame theory and tactics." I have defeated a 2061 USCF as black using only minimal opening theory. He played the Macrozy and I didn't have an opening book, so I took the time to think about the correct moves. My opponent just went along with the ride, and I found some cool ideas that put my opponent into trouble. I eventually won in a crazy (but dead won) queen ending, with my opponent extremely low on time.

I am still going strong with relatively little opening theory. Learning openings further than 7 moves is not really worth the time and effort.

heha, good for you

yes, this is why i post the question in the first place, with the catalan getting more and more popular, it seems become the white main line.  and i guess the more i want to ask is what to play against the catalan? because only play bogo is kind boring

Manatini (Post #29): Yupp, it works ... as long as White doesn't erroneously transpose into the Old Benoni and continues with correct play of 2 e4 cxd4 3 Nf3.
And Shhh .... don't tell the Scandinavians ... they might get the idea of playing ... d5 against 1 e4.