Answer
There are 2 modes, $103˚F$ and $104˚F$.
Work Step by Step
Order the data set from least to greatest:
$74, 91, 96, 103, 103, 103, 104, 104, 104$
From the data above, we can see that $103$ and $104$ were both repeated 3 times, while the rest only repeated once. Therefore there are 2 modes, $103˚F$ and $104˚F$.