A company has a multi-tier application that uses Amazon API Gateway, AWS Lambda, and Amazon RDS. The company wants to investigate a slow response time to calls that come from the API Gateway API.
What is the MOST operationally efficient way for the company to determine which internal call is causing the slow response times?

A. Use Amazon CloudWatch.
B. Use AWS X-Ray.
C. Use AWS CloudTrail.
D. Use VPC Flow Logs.