The notch or depression where the bronchus, the blood vessels and the nerves enter the lung is the:

A. Crackles are discontinuous, short popping sounds that are often heard during inhalation and are typically associated with conditions like pneumonia or pulmonary edema, not asthma.
B. Wheezes are continuous, high-pitched sounds often heard during exhalation and are commonly associated with asthma or other obstructive airway conditions. These sounds are caused by the narrowing of the airways.
C. Stridor is a harsh, high-pitched sound often heard during inhalation and indicates upper airway obstruction, such as in croup or a foreign body in the airway.
D. Rhonchi are low-pitched, gurgling sounds that are often associated with blockages in the larger airways (such as mucus) and are generally heard during both inhalation and exhalation, but they are not typically high-pitched like wheezes.

A. Bronchioles are smaller branches of the bronchial tree that come after the bronchi. They are not formed directly from the trachea.
B. The hilum is a region on the lung’s surface where structures like bronchi, blood vessels, and nerves enter or exit—but it is not a branch of the trachea.
C. The bronchus (plural: bronchi) is one of the two primary branches that the trachea divides into—right and left primary bronchi—which lead into each lung.
D. The conchae (or turbinates) are bony structures inside the nasal cavity that help filter and humidify air, but they are not related to the branching of the trachea.