SAT Question 6989c80a: Linear Functions answer and explanation with Desmos solution

Choice A is correct. It's given that the function $F\left(x\right)=\frac{9}{5}\left(x-273.15\right)+32$ gives the temperature, in degrees Fahrenheit, that corresponds to a temperature of $x$ kelvins. A temperature that increased by $2.10$ kelvins means that the value of $x$ increased by $2.10$ kelvins. It follows that an increase in $x$ by $2.10$ increases $F(x)$ by $\frac{9}{5}\left(2.10\right)$, or $3.78$. Therefore, if a temperature increased by $2.10$ kelvins, the temperature increased by $3.78$ degrees Fahrenheit.