The common bile duct empties into which of the following structures of the gastrointestinal tract?

A. The trachea is the windpipe that carries air to the lungs. While it plays a role in respiration, it does not protect the airway during swallowing.

B. The epiglottis is a flap of cartilage that covers the trachea during swallowing, preventing food or liquid from entering the airway and directing it to the esophagus.

C. The uvula is part of the soft palate that helps in the swallowing process but does not directly protect the airway. It assists in preventing food from entering the nasal cavity.

D. The pharynx is the passageway for both air and food, but it does not provide protection to the airway during swallowing. The epiglottis is the main structure responsible for this protection.

A. The ovaries are responsible for producing hormones such as estrogen and progesterone but do not directly produce lubrication during sexual excitement.
B. The cervix produces mucus that changes in consistency throughout the menstrual cycle but does not play a significant role in lubrication during sexual activity.
C. Skene's glands, located near the urethra, secrete fluid that is often compared to prostate fluid in males, but they do not play the primary role in vaginal lubrication during sexual excitement.
D. Bartholin's glands, located near the vaginal opening, secrete mucus that provides lubrication during sexual excitement, helping to reduce friction and enhance comfort during intercourse.