B at the end of the study, since at the start would be problematic since that’ll make the participants behave differently, during the course will also make them behave differently for the remainder of the study, after publishing will create ethical issues and public problems. Answer is Option B.
crossing over is the exchange of chromosome segment between non sister chromatids in meiosis full stop crossing over create new combination of gene in the gamates that are not found in either parent contributing to genetic diversity.
