When there is a cut in the skin and bacteria enter the body, the immune system responds. First, macrophages approach the area of the cut. Next, the macrophages surround any bacterial cells and engulf them. What feature of the immune system is best described by this scenario? A. the inflammatory barrier, which is a part of innate immunity B. the phagocytotic barrier, which is a part of innate immunity C. antigen specificity, which is a part of adaptive immunity D. self-recognition, which is a part of adaptive immunity

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.