Exam Certified Platform App Builder topic 1 question 99 discussion

So, it shouldn't be B the corect answer. You CAN convert into text, number or email. Then, which is it?

NOT: D. Changing the data type of a field used in a report from text to an encrypted field. "...an existing custom field can’t be converted into an encrypted field nor can an encrypted field be converted into another data type." i.e. it can't be done without deleting and recreating the field which the app builder will NOT be doing. Now it makes sense why those two conditions were put in there...for answers C & D.

NOT: B. Changing the data type of a field used as an External ID from number to text. "If you change the data type of a custom field that‘s set as an external ID, choosing a data type other than text, number, or email causes the field to no longer act as an external ID." This conversion causes no issue with the external id field acting as an external id field, so no extra steps necessary. Therefore, this does not meet the criteria. C. Changing the data type of a field used in an Apex class from number to text. "You can’t change the data type of a custom field referenced by other items in Setup such as Visualforce pages, Apex code, processes, or flows." This would require the extra step of removing all apex references, etc., however, the scenario states that the app builder will NOT delete and recreate any fields, NOR modify any Apex code. In addition, this is the App Builder exam, so it makes sense that the answer doesn't lie here.

If the documentation says: "You can’t change the data type of any custom field that is mapped for lead conversion." Then there are no possible steps for the answer A since the Salesforce won't let you to make even the 1st step which is the conversion itself. In my opinion, the answer is B because 1) it is possible 2) after converting the external ID from number to text, we can still do something with it. Am I missing something?