Alveolar capillaries dilate and bacterial exudate develops; this is which process?

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This describes the early stage of lobar pneumonia, where alveolar capillaries become dilated and an inflammatory exudate rich in bacteria starts filling the air spaces. The dilation of the capillaries increases blood flow to the affected area and allows fluid, cells, and organisms to leak into the alveoli, giving the lung a congested, red, and heavy appearance. This congestion phase is followed, if the process progresses, by the red hepatization and gray hepatization stages as the exudate composition changes (with red blood cells and later more fibrin and leukocytes), and finally by resolution.

The other options point to later phases or a different process. Red hepatization involves alveoli filled predominantly with red blood cells and fibrin, gray hepatization involves disintegrated red cells leaving a fibrinopurulent exudate, and pulmonary edema is accumulation of edema fluid rather than bacterial exudate within alveoli.