Sometimes key "B" doesn't work on my preinstalled keyboard Although I have seen discussions on this topic before here and I tried all those options told by everyone, yet the problem persists with me. 

So here is the thing->-

Its been 3 weeks since I bought a new macbook pro and when I start using it, sometimes keys like B, G, - stopped working eventually and after that I have to press long enough. Sometimes I pressed very hard and then after 4-5 seconds it started responding. But this is not a one-time behaviour. The occurrance of this is 4 times out of 10.

The text to speech service and mouse keys options are disabled already.
Even I posted on apple discussions 
https://discussions.apple.com/thread/5098212

Please help.
Back up your data and take it to the Genius Bar. Since it's less than a month old, it will certainly still have the warranty, so they will either fix or replace for nothing.