To simplify the expression \( \frac{4}{y^{-3}} \), we need to remember that dividing by a negative exponent is equivalent to multiplying by the positive exponent.
First, we can rewrite the expression as follows:
\( \frac{4}{y^{-3}} = 4 \times y^{3} \)
This is because moving \( y^{-3} \) from the denominator to the numerator changes the sign of the exponent from negative to positive.
So, the simplified expression is:
\( 4y^{3} \)
In conclusion, the correct simplification of \( \frac{4}{y^{-3}} \) is \( 4y^{3} \).