The answer is B. - Ivan Pavlov
what they rest of the rest of the sentence Explanation:
Answer: variables
Explanation:
A variable is either a qualitative or quantitative entity for example a number, age, sex, income, days, class grades, color, texture, shape and other. A variable can be changed or manipulated in an experiment to know its impact on the desired variable or the experimental variable.
A variable may vary among the members of the population for example height, weight, age, sex, intelligent quotient and other features. Such variation s can be useful in determination of the most prominent or least occurring traits in the survey research.
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