Explanation
Correct answer: C.
Choice C is the best answer because it presents information that, if true, would coherently and directly account for the researchers’ observation about the LCOE differential between plants using new cells and plants using recycled cells. The text explains that the researchers found that the LCOE—a cost-per-unit electricity measure that includes the cost of acquiring the materials—is higher for plants using new cells than for plants using cells recycled three times, with the gap between them growing from 18.8% to 31.3% when the researchers reduced the modeled cell lifetime by two-thirds (that is, from 15 years to 5 years). If obtaining new cell materials were more expensive than recycling preexisting cell materials, then plants using new cells would incur greater materials costs than plants using recycled cells when cells need to be replaced, and the greater frequency of cell replacement entailed by a shorter cell lifetime would force plants using new cells to incur that greater cost more often—widening the gap between those plants and plants using recycled cells.
Why the other choices are wrong
Choice A
Choice A is incorrect because the information that efficiencies are similar between new and recycled cells (which the text already establishes) and that frequency of recycling doesn’t affect the LCOE for plants using recycled cells wouldn’t address the effect of shorter cell lifetimes on the LCOE of plants using new cells. Information about that effect would be needed to account for the observation that the gap between the LCOEs for the two types of plants widens when cell lifetimes are shortened.
Choice B
Choice B is incorrect. Although the choice does point to the possibility of a scenario that could explain the growth in the LCOE differential (“potentially less expensive than producing new cells”), it presents that information as a concession (“although”) to its central assertion, which is that the cumulative costs would increase if cells had to be replaced more frequently than on the original 15-year timeline. This choice doesn’t indicate whether the increased cumulative costs in question are those of recycled-cell plants or both types of plants; either way, an increase in cumulative costs isn’t a coherent or direct explanation for why the difference in costs between new-cell plants and recycled-cell plants increases when the cell lifetime is reduced by two-thirds. A coherent and direct explanation for growth in the cost difference between the two types of plants must focus on a disparate effect on the plants’ costs; choice B, however, presents information that could be but is not necessarily relevant to a disparate effect and then doesn’t draw the relevant conclusion from it, instead drawing a conclusion about cumulative costs that doesn’t entail a growing differential.
Choice D
Choice D is incorrect because even if plant operating costs increase as cell lifetime decreases, that would be true for plants using new cells and for plants using recycled cells and thus wouldn’t be responsible for a divergence; therefore, the finding wouldn’t coherently and directly explain the observation that the gap between the LCOEs of the two types of plants widens as cell lifetimes are reduced.