The diaphragm contracts during the phase of respiration called:

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. Exhalation is the passive phase of normal breathing and occurs without effort during relaxed respiration. It involves the diaphragm and intercostal muscles relaxing, allowing air to flow out of the lungs.
B. Apnea refers to a temporary cessation of breathing and is not a phase of normal breathing.
C. Inhalation is the active phase of normal, relaxed breathing. It requires energy as the diaphragm contracts and moves downward and the intercostal muscles contract to expand the chest cavity, allowing air to enter the lungs.
D. Expiration is another term for exhalation, which is passive during normal relaxed breathing.