Question

which is the test variable (independent variable) in this experiment? the type of tomato plant used the amount of water given to the plants the six weeks that passed before the plants were measured the type of water given to the plants

Explanation:

An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable. In this case, if we assume the experiment is about how different types of tomato plants respond (the dependent variable would be something like growth, yield etc.), then the type of tomato plant is what the experimenter is changing (the independent variable). The amount of water would be a controlled variable if kept same for all (but if varying, could be independent in a different experiment - but the question is about "this experiment" and the first option is most likely). The time (six weeks) is a constant here (not a variable being tested as independent - it's just the duration of the experiment). The type of water (e.g., tap vs. distilled) - if that was the variable being tested, but the question's context (since first option is about tomato plant type) makes us assume the experiment is about tomato plant types.

Answer:

the type of tomato plant used