Paleontologists at the Montbrook fossil dig typically find the isolated bones and teeth of prehistoric mammals buried at regular intervals; the location of these fossils is evidence
favoring the hypothesis of a prehistoric river fed by a nearby glacier that scattered the mammals’ remains after the decay of their soft tissue.
intended meaning: the location of these fossils, at regular intervals, favors the hypothesis that
a prehistoric river fed by a nearby glacier
scattered the mammals’ remains after the decay of their soft tissue.
in that clause, a prehistoric river is a subject and scattered is a verb in past tense
(A) favoring the hypothesis of a prehistoric river fed by a nearby glacier that
A out since "that" placed after "a nearby glacier" make "scattered" become Verb for "a nearby glacier" and in turn distort the intended meaning
(B) that favors the hypothesis of a prehistoric river that was fed by a nearby glacier and that
(C) favoring the hypothesis that a prehistoric river fed by a nearby glacier
C is much better, more clear and precise in structure.
the hypothesis that clause >> the hypothesis of +N + N modifier
"a prehistoric river fed by a nearby glacier...">"a prehistoric river that was fed by a nearby glacier and that"
Meaning: C focus more on the action of a prehistoric river while B primarily focus on the river.
Because the part before ";" stated about the regular interval of fossils, the second part (after

supposed to explain the "regular interval" that "a prehistoric river scattered the mammals’ remains after the decay of their soft tissue." C is better
(D) in favor of the hypothesis that a prehistoric river was fed by a nearby glacier and that
second that make "scattered" become Verb for "the hypothesis".
"the hypothesis scattered the mammals’ remains after the decay of their soft tissue" does not make sense.
D out
(E) of favor for the hypothesis of a nearby glacier that fed a prehistoric river and
"of favor for" is unidiomatic. more importantly, distorted meaning. E out
Answer: C