You are a forensic scientist. for today, your supervisor tells you to perform a confirmatory test for semen on item d. you recover item d from the evidence locker. item d is a vaginal swab from a sexual assault kit. an ap spot test has already been performed on the swab, with a positive result. you cut off a small portion of the swab. you agitate the swab in a small tube with water. you smear this water onto a microscope slide and stain the slide with red dye and green dye. you look for sperm cells under a microscope, but do not observe any sperm cells. explain.