Coastal restoration workers sometimes add compost to soil to improve plant growth, but transporting large quantities of compost can be costly. Environmental scientist Lena Ortiz and her colleagues grew seaside grass seedlings with different amounts of compost under either fresh-water or saline-water conditions. The researchers concluded that adding 5% compost may be more efficient than adding 10%, particularly in saline environments, because the moderate amount produces most of the improvement in seedling survival.
Which choice most effectively uses data from the graph to support the researchers’ conclusion?