Which of the following best describes the role of pretraining data mixtures in transformer models?
A) They enable the model to be trained on a single, large dataset to improve generalization across all tasks.
B) They allow for the selection of specialized models by combining data from multiple sources, thereby enhancing the model's ability to handle specific tasks or domains.
C) They reduce the need for fine-tuning by training the model on a fixed dataset with limited variability.
D) They simplify the model architecture by integrating various data types into a unified training process.