Bias in choosing and retaining participants in a study is called:

SELECTION BIAS occurs when the participants included in or retained in a study are not representative of the target population — specifically related to HOW participants are selected and retained. Sampling bias is a type of selection bias related to how the sample is drawn. Confounding bias is when a third variable distorts the relationship between exposure and outcome. Measurement/information bias relates to data collection errors. Selection bias is the specific term for participant selection and retention issues. C is correct.