Master-Detail Relationship, the parent field on the child record can be optional.
Since Apex sharing reasons are not available for standard objects, so sharing individual records of standard objects is not possible.
Account object has a custom field 'Tax' of type number. Two account records are present in Salesforce, account name Acc1 has value 7 in this field while account name Acc2 does not have any value in this field. This custom field Tax is now given a default value of 89 by editing it. Which of these cases will happen:
'View All' has been checked at the profile level for a custom object Position. OWD is private of the Position object. A user will be able to view Position records owned by other users.