BCD are right

A is wrong, B is correct.
"In autonomous database, no logins are allowed to the OS. No root or SYSDBA logins are allowed. The only allowed logins are as admin, privileged default autonomous database user, or regular database user."

Answer should be B. C. D

Correct answer is B,C and D

Option A is incorrect as OS logons are not granted with autonomous database

The correct answer is B,C,D

Source: https://www.oracle.com/database/technologies/datawarehouse-bigdata/adb-faqs.html
Note:
How does Oracle Autonomous Database provide data security?
Oracle Autonomous Database protects against both external attacks and malicious internal users:

All data is encrypted at rest using transparent data encryption.Network connections from clients to ADB are also encrypted using the client credentials wallet. Using client credential wallets includes both server and client-side authentication and provides the highest level of security.

Oracle automatically applies all security updates to ensure data is not vulnerable.

Customers are not given OS logons or SYSDBA privileges to prevent phishing attacking.

Additional in-database features such as Database Valut, Virtual Private Database and Data Redaction are also available.