Why Cat Answer You When You Said Meow
Cats try to communicate with human by making sounds, a meow of cat can mean many things.
When cats are feeling good, they will make a short and sweet meow, that is why when you said meow to a cat in a friendly way, they will answer with a short and sweet meow, which is saying thank you for being friendly and tell you that "I like you too".
However, not every times cats will reply you with a sweet meow. Sometimes, cats might reply you with a longer and lower pitch meow. This indicates that the cat is in anger and defensive. Lower pitch meow make cats sound bigger and more threatening.
If this sound is made by a strange car walking and resting out in the neighborhood, you better beware and leave the cat alone.