Answer:
The correct answer will be option- an experimental investigation, because it allows for the control of variables.
Step-by-step explanation:
An experimental investigation is a type of scientific investigation which involves the sequential steps of the scientific method that is from forming a hypothesis and performing controlled experiments including the dependent and independent variables.
Since in the given question, the given statement assumes that adding more salt to water can cause the change in the freezing temperature of the mixture which could be tested only through the experiments.
The experiment is performed in which the amount of salt will be considered independent variable and the freezing temperature would be considered dependent variable.
Since independent variables can be controlled, therefore, the selected option will be the correct answer.