Evaluating the Experiment from the Inside: Internal Validity While Several

Evaluating the Experiment from the Inside: Internal Validity While several mistakes can threaten statistical conclusion validity, the two most common ones are

A) computing too many statistical tests and achieving insufficient statistical power.
B) confounding by extraneous variables and using too many subjects.
C) selecting too extreme a significance level and using the wrong test for experimental data.
D) using too many subjects and achieving insufficient statistical power.