1. The problem asks what the partial derivative $\frac{\partial I}{\partial T}$ represents when $I$ is a function of temperature $T$ and humidity $H$, written as $I = f(T, H)$. 2. The partial derivative $\frac{\partial I}{\partial T}$ measures how the heat index $I$ changes as temperature $T$ changes, while keeping humidity $H$ constant. 3. This means we look at the effect of temperature alone on the heat index, ignoring any changes in humidity. 4. The options given are: - A: Overall change when both $T$ and $H$ change (this is the total derivative, not partial). - B: Rate of change of $I$ with respect to $T$ while $H$ is constant (this matches the definition of partial derivative). - C: Temperature at which heat index is highest (this is a maximum, not a derivative). - D: Rate of change of $I$ with respect to $H$ while $T$ is constant (this is $\frac{\partial I}{\partial H}$, not $\frac{\partial I}{\partial T}$). 5. Therefore, the correct interpretation is option B. Final answer: **B. The rate of change of the heat index with respect to temperature, while humidity is held constant.**