The question relates to the understanding of river channel planforms and their relationships with sinuosity and channel slope. Let's analyze and explain each option to determine the correct answer.

The graph provided shows sinuosity on the y-axis and slope (%) on the x-axis. River channels generally fall into three categories based on their planforms: straight, meandering, and braided.

1. Straight Channel: A straight channel typically exhibits a low sinuosity, often close to 1. In the graph, this corresponds to area A where the sinuosity is about 1.1 and the slope is relatively low.
2. Meandering Channel: Meandering channels display higher sinuosity due to their winding paths. This is depicted by area B on the graph, where sinuosity is at its peak though the slope remains moderate.
3. Braided Channel: These channels have multiple interweaving paths, showing increased complexity. They often have a higher slope and lower sinuosity compared to meandering channels. In the graph, area C represents this scenario with a decreasing sinuosity as the slope increases towards 2%.

Based on these analyses:

• Option 1: A is straight channel; B is meandering and C is braided — This correctly matches the characteristics of the channels with the corresponding areas on the graph.
• Option 2, 3, and 4 do not correspond accurately with the characteristics shown in the figure for each type of channel.

Hence, the correct answer is:

A is straight channel; B is meandering and C is braided.