Aphids are eating Jan's Peace roses. She wants to test some household chemicals to see if they will kill the aphids. She used bleach, ammonia, and dishwashing liquid in equal amounts. She will evaluate the aphid population after one week to see which chemical killed the most aphids. Which is the independent variable? A. Number of roses on the plant B. Kinds of chemicals used. C. Number of aphids killed. D. The kind of rose

In an experiment, independent variables are those which are changed or manipulated to find the value of dependent variables. Here number of roses is dependent variable because its number depends on how many aphids are present. So option A is incorrect. Kinds of aphids killed is also dependent variable, because its population depends on how much chemical is sprayed to kill it. So, option C is also incorrect. Kind of rose is irrelevant, because aphids will eat any kind of rose. So the right answer is - Option B, kinds of chemicals used. This is because it will determine the number of aphids left and population of roses.