Some of the threats to internal validity in research are:

A) Quasi experimental design

B) Pre-Testing

C) Attrition

D) History

E) Maturation

Choose the correct answer from the options given below semi colon:

The correct answer is C, D and E only.

Internal validity refers to the degree of confidence that a causal relationship being tested is trustworthy and not influenced by other factors or variables. In research, threats to internal validity are factors that can compromise the confidence in saying that a relationship exists between an independent and a dependent variable. Let us analyze the given options to identify the threats:

A) Quasi-experimental design: This is a type of research design, not a threat to internal validity. Although quasi-experimental designs may have more inherent vulnerabilities than true experimental designs, the design itself is a method rather than a threat.

B) Pre-Testing: While pre-testing can sometimes cause a testing effect (where taking a pre-test affects performance on a post-test), pre-testing itself is a common research procedure rather than an inherent threat to internal validity. The actual threat is called "testing effect" or "testing threat."

C) Attrition (Mortality): This is a major threat to internal validity. It occurs when participants drop out of a study over time. If the dropout rate is high or systematic (e.g., participants in one group drop out more than in the other), it can bias the final results and affect the comparability of the groups.

D) History: This is a threat to internal validity that refers to specific events occurring between the first and second measurement (or during the course of the study) that are not part of the experimental treatment but can influence the participants' responses or behaviors.

E) Maturation: This refers to natural changes or processes that occur within the participants over time (e.g., growing older, becoming tired, hungry, or more experienced) which might influence the dependent variable independently of the treatment.

Therefore, among the choices listed, Attrition (C), History (D), and Maturation (E) are classic, direct threats to internal validity, making C, D and E only the correct response.