Consider the following statements related to pore pressure parameters, $A$ and $B$:
- $A$ always lies between $0$ and $1.0$
- $A$ can be less than $0$ or greater than $1.0$
- $B$ always lies between $0$ and $1.0$
- $B$ can be less than $0$ or greater than $1.0$
For these statements, which of the following options is correct?
- P and R
- P and S
- Q and R
- Q and S