When the conditions of a study resemble or approximate only the conditions of interest, questions may be raised about the ''blank'' of the study.

A external validity
B internal validity
C standardization
D randomization

This question is very difficult for me. I can't find exactly the right answer in my text book. I believe is A but I'm not at all sure.

I think you're right.

http://www.gifted.uconn.edu/siegle/research/Samples/externalvalidity.html

To determine the correct answer, we need to understand the terms related to experimental research design.

External validity refers to the extent to which the results of a study can be generalized to real-world settings or populations beyond the specific conditions of the study. It questions whether the findings can be applied to other situations or groups.

Internal validity refers to the degree to which a study provides accurate and trustworthy results by minimizing confounding variables. It focuses on how well the study design enables researchers to draw causal conclusions about the relationship between variables.

Standardization refers to the uniformity and consistency in the administration of research procedures, treatments, and measurements. It ensures that all participants receive the same instructions and experiences throughout the study.

Randomization refers to the process of randomly assigning participants to different experimental conditions. It helps control for potential biases and ensures that participants have an equal chance of being assigned to any condition.

Based on the information provided, when the conditions of a study resemble or approximate only the conditions of interest, the question raised is about the external validity of the study (option A). External validity is concerned with whether the findings can be generalized to other settings or populations beyond the specific conditions of interest.

Therefore, your initial intuition is correct, and the answer is A - external validity.