In an experiment plants are fed once daily for one week. there are four plants the first is given oil, the second one vinegar, third one water and fourth one sugar. what is the manipulated variable?

Why is it important for scientists to review and repeat the work of other scientists? 1.a scientific theory must be tested three times before it is proven. 2.the scientific method only applies to repeated experiments. 3.an experiment may have had errors that the scientists didn't recognize. 4.the results of individual scientists may be influenced by bias. 5.an experiment must be performed twice before the data can be analyzed.