Explanation
Correct answer: A.
Choice A is the best answer. The convention being tested is subject-modifier placement. This choice makes the noun phrase “researcher Robert Losey” the subject of the sentence and places it immediately after the modifying phrase “since…Siberia.” In doing so, this choice clearly establishes that researcher Robert Losey—and not another noun in the sentence—is who uncovered fragments of a 2,000-year-old reindeer training harness in northern Siberia.
Why the other choices are wrong
Choice B
Choice B is incorrect because it results in a dangling modifier. The placement of the noun phrase “researcher Robert Losey’s argument” immediately after the modifying phrase illogically suggests that the “argument” is what uncovered fragments of a 2,000-year-old reindeer training harness in northern Siberia.
Choice C
Choice C is incorrect because it results in a dangling modifier. The placement of the noun “domestication” immediately after the modifying phrase illogically suggests that “domestication” is what uncovered fragments of a 2,000-year-old reindeer training harness in northern Siberia.
Choice D
Choice D is incorrect because it results in a dangling modifier. The placement of the noun phrase “the argument” immediately after the modifying phrase illogically suggests that the “argument” is what uncovered fragments of a 2,000-year-old reindeer training harness in northern Siberia.