Bentuk sederhana dari 6p⁻² . q⁻⁵ . r³ / 2p⁻³ . q⁻⁷ . r⁴ adalah ....

The given expression is:

$$\frac{6p^{-2} \cdot q^{-5} \cdot r^3}{2p^{-3} \cdot q^{-7} \cdot r^4}$$

We can rewrite this as a product of fractions for each component:

$$\left(\frac{6}{2}\right) \cdot \left(\frac{p^{-2}}{p^{-3}}\right) \cdot \left(\frac{q^{-5}}{q^{-7}}\right) \cdot \left(\frac{r^3}{r^4}\right)$$

$$3 \cdot p \cdot q^2 \cdot r^{-1}$$

Using the rule $a^{-n} = \frac{1}{a^n}$, we can write $r^{-1}$ as $\frac{1}{r}$.
So the expression becomes:

$$3pq^2 \cdot \frac{1}{r} = \frac{3pq^2}{r}$$

The simplified expression is $\frac{3pq^2}{r}$, which matches option D.

The final answer is $\text{D. } \frac{3pq^2}{r}$.