Which data type change will require the app builder to perform the additional steps in order to retain existing functionalities? the app builder needs to change the data types of new custom fields. the app builder is not able to delete and recreate any of the fields, nor modify any apex code.

a. changing the data type of a field used in an apex class from number to text.
b. changing the data type of a field used in a report from a text to an encrypted field
c. changing the data type of a field used as an external id from number to text.
d. changing the data type of a field used in lead conversion from number to text