How should you have users upload images?

You have developed an application using Cloud ML Engine that recognizes famous paintings from uploaded images. You want to test the application and allow specific people to upload images for the next 24 hours. Not all users have a Google Account .

How should you have users upload images?
A . Have users upload the images to Cloud Storage. Protect the bucket with a password that expires after 24 hours.
B. Have users upload the images to Cloud Storage using a signed URL that expires after 24 hours.
C. Create an App Engine web application where users can upload images. Configure App Engine to disable the application after 24 hours. Authenticate users via Cloud Identity.
D. Create an App Engine web application where users can upload images for the next 24 hours. Authenticate users via Cloud Identity.

Answer: B

Explanation:

https://cloud.google.com/blog/products/storage-data-transfer/uploading-images-directly-to-cloud-storage-by-using-signed-url