Final answer:
Ephemeral streams best describe most stream channels in an arid environment, characterized by intermittent flow after rainfall events. Braided river descriptions include sand deposits and cross-bedding.
Step-by-step explanation:
The term that most accurately describes most stream channels in an arid environment is a. Ephemeral streams. These streams only flow for a short period of time, often following rainfall. Arid regions lack the consistent precipitation that would support perennial streams, which flow continuously throughout the year. Instead, ephemeral streams typically have an intermittent flow that corresponds with the infrequent and unpredictable rain events in these dry environments.
As for the descriptions given about different environments, i. Mostly sand deposits with some sediment beds having a layer of gravel on the bottom and cross-bedding, are characteristics of a braided river.
Braided rivers have multiple intertwining channels that are often formed in environments with a large supply of sediment. Water flow in braided rivers separates into multiple shallow channels that rejoin and separate again, creating an ever-changing network of waterways. In contrast, swamps and wetlands are ecosystems that have consistent water coverage and support marshy plant life, which is not described here.