The correct answer is A because each foundation model on Amazon Bedrock (e.g., Claude, Titan, Mistral, Meta Llama) has a different maximum token limit, which defines the maximum number of tokens the model can accept in the prompt and generate in the response.

From AWS documentation:

"Each model in Amazon Bedrock has its own maximum token limit. Prompts exceeding the limit must be truncated or adjusted depending on the selected model."

Explanation of other options:

B. On-demand inference support is a platform feature that is uniformly supported across models on Bedrock.

C. All Bedrock LLMs support randomness control through temperature and top-p parameters.

D. Amazon Bedrock Guardrails are designed to work across supported models, though specific behaviors may vary slightly.

Referenced AWS AI/ML Documents and Study Guides:

Amazon Bedrock Model Comparison Guide

AWS Prompt Engineering and LLM Deployment Documentation

AWS ML Specialty Study Guide – Bedrock Model Capabilities