To create an exponential function to model the decay of a substance that decays at a rate of 6% each year, we start with the initial amount and determine the decay factor.
- Initial amount: 600 grams
- Decay rate: 6% means that each year, 94% of the substance remains (100% - 6% = 94%).
The decay factor can be expressed as a decimal:
\[ \text{Decay factor} = 1 - 0.06 = 0.94 \]
Now, we can use the general formula for exponential decay:
\[ f(x) = A \cdot (r)^x \]
where:
- \( A \) is the initial amount,
- \( r \) is the decay factor,
- \( x \) is the number of years.
Substituting in the values we have:
\[ f(x) = 600 \cdot (0.94)^x \]
Therefore, the correct exponential function that models the decay of the substance is:
\[ \boxed{600(0.94)^x} \]