Answer:
herbicide ZWD10
Explanation:
Independent variable in an experiment are defined as the variable that can be changed or controlled as per the requirement of the experiment to determine its effect on the dependent variable.
In the given experiment, herbicide ZWD10 is an independent variable as it's quantity in experiment can be changed or controlled and we are looking for its effect on corn growth which is a dependent variable.
Hence, the correct answer is herbicide ZWD10.
