Major configuration changes within an application should entail new BCDR testing. Any major configuration change or update represents a significant shift in an environment, and, as such, proper testing is needed to ensure that all BCDR implementations and procedures are both still valid and still work as intended. the changes mentioned in the other answer choices are either minor or personnel changes that do not require new comprehensive testing.

I would agree more with A as an answer if the scenario stated it was a major functional change. Since majority functional changes could introduce dependencies or single points of failure which wasn't included in the initial BCDR plan. Just making a functional change is insufficient to retest the BCDR plan IMHO.

A is the correct answer to this question

From experience - you do not test BCDR after every functional change, but if regulator requires you to test particular environment semi annually instead of annually (for highly regulated institution) you must comply

Personally I think B is the most appropriate answer here, I disagree with C & D and I don't think any simple functional change should trigger BCP retesting. It should perhaps trigger BCP plan changes based on changes to that application's BIA if the new functionality makes the application more or less critical to the organisation however.

Disagree with this answer. From practical exp, if it's a monolithic application and IaaS/PaaS then any application change will not require BCDR test as the infra layer or DR would have been the same. SImilarly containers and SaaS app change/update/config change also should not require BCDR test. Regulation change can be valid reason for BCDR test. Somebody commented here about RTO sarcastically but those RPO/RTO changes could be internal rules/policy with BCDR and definitely may require "next" DR test to test /confirm the new targets. More regulations can be state or Federal Govt restrictions for e.g. about failover from Govt DC to happen only to other DCs within certain geographical perimeter. Like many other ISC question, language of this question also rather vague. ISC may expect answer for this as Application change but that's not something ideally trigger this.

This question has a few potentially correct answers. Even a change in staff, if those are the staff who need to perform the BC/DR procedures, would trigger the need for testing, with the new staff involved.

Each time Application changes the design is changed, it can be called for a BCDR Test.

For me it's D, change in regulation may invole major change regarding metrics of BCDR