Questions: Epistaxis is: mouth ulcer cough abnormal respiratory sound nose bleed

The answer is the fourth one: nose bleed.

Explanation for each option:

• Mouth ulcer: This is a sore or lesion that occurs in the mouth, not related to epistaxis.
• Cough: This is a reflex action to clear the airways of mucus or irritants, not related to epistaxis.
• Abnormal respiratory sound: This refers to unusual sounds heard during breathing, such as wheezing or crackles, not related to epistaxis.
• Nose bleed: This is the correct definition of epistaxis, which is bleeding from the nose.

In summary, epistaxis refers to a nose bleed.