The options in this question are not given; here is the complete question:
A medical researcher measures the increase in heart rate of patients under a stress test. What kind of variable is the researcher studying?
A. Identifier
B. Categorical
C. Quantitative
D. Qualitative
The answer to this question is C. Quantitative
Step-by-step explanation:
In research, a quantitative variable refers to a variable or factor that involves using numbers, percentages, and in general, quantities to be understood. Moreover, this is the opposite of qualitative variables that involve using qualities. The medical research described includes a quantitative variable because heart rate can only be measured and understood through numbers. Also, other types of variables such as qualitative or categorical are not involved because these are related to qualities rather than numbers.