A Database Specialist is creating a new Amazon Neptune DB cluster, and is attempting to load data from Amazon S3 into the Neptune DB cluster using the Neptune bulk loader API. The Database Specialist receives the following error:
"Unable to connect to s3 endpoint. Provided source = s3://mybucket/graphdata/ and region = us-east-1. Please verify your S3 configuration."
Which combination of actions should the Database Specialist take to troubleshoot the problem? (Choose two.)

A. Check that Amazon S3 has an IAM role granting read access to Neptune
B. Check that an Amazon S3 VPC endpoint exists
C. Check that a Neptune VPC endpoint exists
D. Check that Amazon EC2 has an IAM role granting read access to Amazon S3
E. Check that Neptune has an IAM role granting read access to Amazon S3