Under the U.S. Aids to Navigation System on the Western Rivers, passing daymarks on the left descending bank are __________.

Correct Answer: Option B — red triangles

Western Rivers navigation rules dictate that passing daymarks on the left descending bank are red triangles. Unlike the IALA system, the Western Rivers system uses specific shapes and colors to denote the bank side, with red triangles marking the left descending bank and green squares marking the right.