To be able to order the given amounts of fluid, we simply have to convert all of them to a common unit.
(a) 3.8 pt (1 qt / 2 pt) = 1.9 qt
(b) 0.6 gal (4 qt / 1 gal) = 2.4 qt
(c) 1.9 L (1 qt / 0.95 L) = 2 qt
Arranging them from greatest to least will give us the answer of
0.6 gal, 1.9 L, 3.8 pt