Abiology student is studying ways to grow crops in soils that are high in salts and other dissolved solids. to determine whether corn plants can tolerate salty soil conditions, she grows one corn plant in typical non-salty soil and one corn plant in the same soil plus 0.5 kilograms of salt. after 6 weeks of growth, the corn plant grown in salty soil is only about 50% of the mass and height of the corn plant grown in non-salty soil. how can this research be improved so that she will have greater confidence in her data? a) repeat the experiment but with additional corn plants to increase the sample size b) add more salt to the experimental condition so that the resulting data is more clear c) test an additional variable such as amount of moisture so that the results are more valid d) revise the original hypothesis to account for the fact that plants do not grow in salty soils