A- Many people hate this question, but i love it, every time someone asks me that, i see a non practicioner getting intrested in the art, and NO, Jiu Jitsu is a grappling art, while Karate is a strinking art.
A- This is one of the most common reasons why people don't start BJJ, they fear the injury, they fear the agressiveness of their partner while training, and it is a real concern, but let me tell you that once you get caught in a submission, being a joint lock, or any kind of choke, all you need to do is TAP, tap soon, tap often, thats the key to go 100% and still manage the injury risks.
A- The TAP is the main and only way we can train and go hard 100% while keeping the injuries at a the lowest rate possible, it can be done by tapping 3 times on the body of your training partner, on the mat even verbally, one that does not respect the TAP, does not respect the art, simple put.
A- Yes, BJJ or better put Gracie Jiu Jitsu is one if not the most effective way to protect yourself against a stronger and larger opponent, BUT you do need to understand that there is not a" one answer to all " when it comes to self defense, so you can add BJJ to your knowledge, for sure will give you a great headstart, even if you already know and train other martial arts.