What is the pathophysiology of edema?

Edema is caused by an increase in net fluid filtration from the vascular bed, which depends on changes in Starling's forces.
Other factors include compensatory renal retention of sodium and water, venous and lymphatic flow efficiency, and capillary flow regulation through precapillary sphincters.
Edema is always localized and related to a focal process, such as lymphatic obstruction or insect bites.
Edema can be localized, regional, or generalized, and generalized or peripheral edema is often due to a systemic process, such as congestive heart failure.
a) Only statements 1 and 2 are correct.
b) Only statements 2 and 4 are correct.
c) Only statements 1, 2, and 4 are correct.
d) All statements are correct.