6. There are __ common navigation lights that must be displayed from sunset to sunrise and during periods of restricted visibility, such as fog. a two three C four

## Step 1<br />This problem is related to maritime navigation and the rules and regulations governing it. Specifically, it is about the navigation lights that must be displayed from sunset to sunrise and during periods of restricted visibility such as fog.<br />## Step 2<br />According to the International Regulations for Preventing Collisions at Sea (COLREGS), there are three common navigation lights that must be displayed from sunset to sunrise and during periods of restricted visibility such as fog.