Explanation
How can an architect achieve this
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_per ms_enforcing.htm Example: To check the field-level read permission of the contact's email field before querying for this field:
if (Schema.sObjectType.Contact.fields.Email.isAccessible()) {
Contact c = [SELECT Email FROM Contact WHERE Id= :Id];
}
Answer for B -
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_key words_sharing.htm The "with sharing" keyword allows you to specify that the sharing rules for the current user are considered for the class. You have to explicitly set this keyword for the class because Apex code runs in system context. In system context, Apex code has access to all objects and fields- object permissions, field-level security, sharing rules aren't applied for the current user. This strategy ensures that code doesn't fail to run because of hidden fields or objects for a user.