A company collects data from a large number of participants who use wearabledevices.

This option is the most efficient because it uses provisioned mode, which is a read/write capacity mode for processing reads and writes on your tables that lets you specify how much read and writethroughput you expect your application to perform1. It also specifies the read capacity units (RCUs) and write capacity units (WCUs), which are the amount of data your application needs to read or write per second. It also meets the requirement of staying at or below its forecasted budget for DynamoDB, as provisioned mode has lower costs than on-demand mode for predictable workloads. This solution meets the requirement of collecting data from a large number of participants who use wearable devices with a constant and predictable data workload. Option A is less efficient because it uses provisioned mode and DynamoDB Standard-Infrequent Access (DynamoDB Standard-IA), which is a storage class for infrequently accessed items that require milliseconds latency2. However, this does not meet the requirement of collecting data from a large number of participants who use wearable devices with a constant and predictable data workload, as DynamoDB Standard-IA is more suitable for items that are accessed less frequently than once every 30 days. Option C is less efficient because it uses on-demand mode, which is a read/write capacity mode that lets you pay only for what you use by automatically adjusting your table’s capacity in response to changing demand3. However, this does not meet the requirement of staying at or below its forecasted budget for DynamoDB, ason-demand mode has higher costs than provisioned mode for predictable workloads. Option D is less efficient because it uses on-demand mode and specifies the RCUs and WCUs with reserved capacity, which is a way to reserve read and write capacity for your tables in exchange for discounted hourly rates. However, this does not meet the requirement of staying at or below its forecasted budget for DynamoDB, as on-demand mode has higher costs than provisioned mode for predictable workloads. Also, specifying RCUs and WCUs with reserved capacity is not possible with on-demand mode, as it only applies to provisioned mode.