While proceeding downriver, you sight a red triangular-shaped daymark on the left bank. Under the U.S. Aids to Navigation System on the Western Rivers this is a __________.

Correct Answer: Option B — passing daymark

On the Western Rivers, a red triangular daymark on the left bank is a passing daymark. These marks are used to guide vessels along the channel. Because the left bank is the green side, a red mark here serves as a specific navigational aid for vessels descending the river.