What is happening?

John is upgrading a cluster from NGX R65 to R76. John knows that you can verify the upgrade process using the pre-upgrade verifier tool.

When John is running Pre-Upgrade Verification, he sees the warning message:

Title: Incompatible pattern.

What is happening?
A . R76 uses a new pattern matching engine. Incompatible patterns should be deleted before upgrade process to complete it successfully.
B . Pre-Upgrade Verification process detected a problem with actual configuration and upgrade will be aborted.
C . Pre-Upgrade Verification tool only shows that message but it is only informational.
D . The actual configuration contains user defined patterns in IPS that are not supported in R76. If the patterns are not fixed after upgrade, they will not be used with R76 Security Gateways.

Answer: D