Explanation:

While Mississippi forms a bird foot delta, the Sundarbans are an example of an arcuate river delta: This statement is correct. The Mississippi River delta is an example of a birdfoot delta, characterized by multiple distributaries resembling bird's toes. The Sundarbans delta, formed by the Ganges-Brahmaputra river system, is an example of an arcuate or fan-shaped delta.

The river should have a long course to form a delta: This statement is  correct. Deltas often form in areas where rivers meet an ocean or lake, and the river's velocity decreases, leading to the deposition of sediment. This process is more likely to occur in rivers with longer courses.

The size of the delta is independent of rock characteristics: This statement is incorrect. The size and shape of a delta can be influenced by various factors, including the type of rocks and sediments the river encounters, the river's gradient, and the energy of the receiving basin. These factors can impact the rate of sediment deposition and the overall formation of the delta.