Relationship among details

Untimed practice

Question 1

Horticulturists have investigated whether reflective ground covers can help young plants receive light on the shaded sides of their leaves. In a greenhouse, researchers placed reflective covers beneath 10 of 20 genetically similar seedlings and dark covers beneath the other 10. After four weeks, seedlings above reflective covers had gained a median of 32 grams of dry mass, whereas seedlings above dark covers had gained 20 grams. The seedlings were grown under one greenhouse lighting schedule and were not followed beyond the four-week period. The experiment suggests that reflective ground covers can increase short-term growth under the tested greenhouse conditions.

Which choice best describes the relationship between the study’s intervention and its measured outcome?

AThe researchers varied seedling mass and measured which ground cover formed underneath each plant. BThe researchers varied the type of ground cover and measured seedling dry-mass gain. CThe researchers deliberately varied both the ground-cover type and the seedlings’ final mass. DThe researchers only recorded the covers already used by growers and did not assign cover types.

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