An AWS Solution architect who uses EBS General Purpose SSD (gp2) volume type for his EBS volumes now wants to modify some of these volumes. What options would you suggest? (Select TWO)

Answer options:

A.A 50GB gp2 root volume can be modified to an EBS Provisioned IOPS SSD (io1) after stopping the instance.
B.A gp2 volume attached to an instance as a root volume can be modified to a Throughput Optimized HDD (st1) volume.
C.A 1GB gp2 volume attached to an instance as a non-root volume can be modified to a gp4 volume.
D.A 1TB gp2 volume attached to an instance as a non-root volume can be modified to a Throughput Optimized HDD (st1) volume without stopping the instance or detaching the volume.

Correct AnswerA, D
The EBS volume types can be modified in flight without the volume being detached or the instance being restarted. However, some limitations need to be noticed. The details are in https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/modify-volume-requirements.html
Option A is CORRECT: Because the root volume can be changed to io1 such as:
Option B is incorrect: Because a gp2 volume that is attached to an instance as a root volume cannot be modified to an st1 or sc1 volume. Check https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/modify-volume-requirements.html.
Option C is incorrect: Because there is no gp4 type of volume available.
Option D is CORRECT: Because the volume size 1TB is suitable for Throughput Optimized HDD (st1):