Sperm must travel to the distal end of the uterine tube to encounter the egg before it dies.

A. Esophageal glands secrete mucus to lubricate the esophagus, but they do not cause acid reflux.

B. Pharyngeal constrictors are muscles that help in the swallowing process, not in preventing acid reflux.

C. The lower esophageal sphincter (LES) is a ring of muscle that controls the passage of food from the esophagus to the stomach. If the LES is weakened or relaxes inappropriately, stomach acid can flow back into the esophagus, causing acid reflux or "heartburn."

D. The upper esophageal sphincter controls the passage of food from the pharynx into the esophagus, but it is not involved in preventing acid reflux.

A. Two haploid (n) cells; four haploid (n) cells: At the end of meiosis I, the result is two haploid cells, each with half the number of chromosomes of the original cell. At the end of meiosis II, these two haploid cells divide again to form a total of four haploid cells.

B. Two diploid (2n) cells; one haploid (n) cell: This option is incorrect because meiosis I produces two haploid cells, not diploid cells, and meiosis II produces four haploid cells, not one.

C. Two diploid (2n) cells; four haploid (n) cells: This option is incorrect because meiosis I does not produce diploid cells; it produces two haploid cells. At the end of meiosis II, the result is four haploid cells, which is correct, but the description of meiosis I is incorrect.

D. Two haploid (n) cells; one diploid (2n) cell: This is incorrect because meiosis I results in two haploid cells, and meiosis II results in four haploid cells, not one diploid cell.