Why am I skinny but not showing six-pack abs?

Will I lose weight and get visible six-pack abs by running four times a week?

What does 18% body fat look like on a female?

Why aren’t my six-pack abs flat?

Why can I feel my six-pack abs but not see them?

Why do I only have two abs?

What does 12% body fat look like on a female?

Will 100 sit-ups a day tone my stomach?

Why do I have seven-pack abs?

Why do I gain muscle so slowly as a female?