Answer:
m = 57t, where the units of measurement of 57 are mph and that of t is hr.
Step-by-step explanation:
Use the given info to find the speed of the train, which is a unit rate:
 95 miles      95 mi
------------------ Â = ------------- = 0.95 mile/min
1 hr 40 min    100 min
Better yet, use hours, not minutes.
 95 miles      95 mi
------------------ Â = ------------- = 57 mph
1 hr 40 min    1 2/3  hr
Then m(t) = (rate)(time) = (57 mph)t   This corresponds to Answer D.