Why do we only use the five kinematic equations/where do they come from?

Correct answers A, C, D. The reason B is wrong and A is correct is because the kinematic equations didn’t just appear! They were derived using basic calculus. The kinematic equations are just a simplified version of calculus that we use. We use these specific equations because they tell us the relationship between all the important variables of distance, speed, acceleration and time, which is why C is correct. Lastly, D is correct because if you know calculus, then you don’t have to use the kinematic equations!