Final answer:
The vocal folds in humans are protected from external trauma by mucus, which is produced by the lining of the larynx and traps debris and pathogens, with cilia then moving it away from the lungs.
Step-by-step explanation:
The vocal folds, also known as vocal cords, in humans are protected from external trauma mainly by a combination of structures and substances, one of which is mucus. Mucus is a sticky, moist substance produced by goblet cells in the pseudostratified ciliated columnar epithelium lining the superior portion of the larynx. This mucus serves to trap debris and pathogens, preventing them from causing harm. Additionally, the mucus along with trapped particles is moved upwards towards the laryngopharynx by coordinated movements of cilia. These hair-like projections beat in waves, effectively sweeping mucus and its trapped contents away from the lungs toward the throat, where it can be swallowed or expelled from the body. Hence, the correct answer to the question 'The vocal folds in humans are protected from external trauma by...’ is B) Mucus.