Answer - B.
The AWS Documentation mentions the following.
Kinesis Data Firehose can invoke your Lambda function to transform incoming source data and deliver the transformed data to destinations.
You can enable the Kinesis Data Firehose data transformation when you create your delivery stream.
Option A is incorrect because SQS is a queue service and can not transform the data.
Option C is incorrect because although with EC2 instances, you can achieve the desired result, you need to manage and provision the server.
Lambda is a better option.
Option D is incorrect because an API gateway is used to make API calls and not transform it.