Let's solve this problem by setting up an equation.

Let:
- $x$ = number of pencils bought
- $y$ = number of notebooks bought

We know:
- Each pencil costs $N3.00$, so the total cost for pencils is $3x$.
- Each notebook costs $N5.00$, so the total cost for notebooks is $5y$.
- The total amount spent is $N25.00$.

The equation is:
$$3x+5y=25$$

To find the number of pencils ($x$), we need to solve this equation with possible integer values of $y$.

Case 1: $y=1$
$$3x+5(1)=25⟹3x+5=25⟹3x=20$$
$x=\frac{20}{3}$ (Not an integer, so not possible)

Case 2: $y=2$
$$3x+5(2)=25⟹3x+10=25⟹3x=15$$
$x=\frac{15}{3}=5$ (This is an integer, so it's possible)

Thus, $x=5$.

Therefore, the number of pencils bought is B. 5.