Not as much as I say every day.

If it is changed to "1/5 for moving this pile of coal every day on average", it will be right.

mistake

Except 0

3. Right

Two adjacent natural numbers (non-zero) coprime

4. Wrong

There are countless

5. Wrong

There is no need for prime numbers, as long as the numerator and denominator are mutually prime.

For example: 4/9, the numerator and denominator are not prime numbers, but 4/9 is the simplest fraction.