Final answer:
To improve fault tolerance of an application, deploying resources across multiple Availability Zones is the recommended strategy as it helps in maintaining service if one zone fails.
Step-by-step explanation:
To increase the fault tolerance of an application, the best practices involve deploying resources across multiple layers of redundancy. Here are the options explained:
- C. Deploying resources across multiple Availability Zones: This will ensure that if one availability zone goes down, the others can handle the load, thus improving fault tolerance.
- A. Deploying resources across multiple edge locations: This mainly improves content delivery performance and resilience against DDoS attacks.
- B. Deploying resources across multiple VPC's: While this can create network isolation for different parts of your application, it's not directly related to fault tolerance of the application itself.
- D. Deploying resources across multiple AWS Accounts: This adds a layer of administrative isolation which could be beneficial for security and organizational purposes, but is not the main strategy for increasing application fault tolerance.
So, of the four options provided, the most effective for increasing fault tolerance would be deploying resources across multiple Availability Zones.