Ap bio questions! HELP!!?

Which of the following is not considered a reproductive isolating mechanism? A. sterile offspring B. Ecological offspring C. Feeding behavior D. Gametic imcompatibility E. Timing of courtship display 2. Which of the following best describes what occurs when two species hybridize and a fraction of the hybrids manage to backcross with one of the parent species? A. Introgression B. genetic drift C. Differential reproduction D. Heterozgote E. Random rating