Scientists designed an experiment to determine if the transfer of a drought tolerant gene into a species of wheat plant was successful. They exposed 5,000 genetically modified wheat plants to drought conditions. The scientists also exposed 5,000 regular, unaltered wheat plants to drought conditions. They compared the amount of grain produced by each group of plants to see if the genetically modified wheat had higher yields than the regular wheat plants. What part of the experiment served as the dependent variable?

the number of plants
the number of plants

the amount of grain produced
the amount of grain produced

the regular wheat exposed to drought conditions
the regular wheat exposed to drought conditions