Question

in the respiratory system diagram, b is... the lungs. the bronchi. the diaphragm. the bronchioles.

Explanation:

In the respiratory system, the diaphragm (labeled B in typical diagrams) is a muscle that plays a key role in breathing by contracting and relaxing to change thoracic volume. The lungs are the main organs for gas exchange, bronchi are air passages branching from the trachea, and bronchioles are smaller branches of bronchi. So B corresponds to the diaphragm.

Answer:

the diaphragm.