A college psychology professor who gives a test every two weeks illustrates the process of O a. fixed-interval schedule (FI).
b.
variable-interval schedule (VI).
O c. variable-ratio schedule (VR).
Od.
fixed-ratio schedule (FR).

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.