A quantity is modeled by the function $Q(t)=A(B{)}^t$, where $t$ represents time in years and $A$ and $B$ are positive constants. Which of the following statements must be true?

I. If $B>1$, the quantity is increasing over time.
II. The initial quantity at $t=0$ is $A$.
III. If $0<B<1$, the quantity decreases over time.