The model lacks sufficient depth to capture the complexity of the data, especially with the inclusion of social media trends which introduce high variability.

The quality of the data being used is not up to the required standards, possibly due to inconsistent data collection methods across different regions.

The data was not split correctly during the model's training, evaluation, validation, and testing phases, leading to overfitting on the training dataset.

The model has not undergone retraining to adapt to new market data, causing it to become less accurate as market conditions evolve.

Both A and D are correct, as the model's inability to capture data complexity and lack of retraining contribute equally to the accuracy decline.