A fine-grained bed of an ephemeral lake in a desert is known as a playa. Playas are flat, dry lake beds or basins that are typically found in arid or semiarid regions. They are formed when water collects in depressions on the desert surface, usually during periods of heavy rain or seasonal flooding.

Option 1: Playa - This is the correct answer. A playa refers to the fine-grained bed of an ephemeral lake in a desert. Playas are important features in desert ecosystems, as they can provide temporary habitats for plants, animals, and migrating birds.

Option 2: Oasis - An oasis is a fertile area in the desert where water is present. It usually consists of a water source, such as a spring or well, which supports the growth of vegetation. Unlike a playa, an oasis is a permanent or semi-permanent feature and not specifically associated with a fine-grained lake bed.

Option 3: Drumlin - A drumlin is an elongated landform that is usually formed by glacial action. It has a smooth, rounded shape with one steep and one gentle slope. Drumlins are not related to fine-grained lake beds in deserts.

Option 4: Natural levee - A