Under current Salesforce permission-set behavior, option A is the valid configuration among the choices provided. Account Forecasting objects require the Manufacturing Account Forecast PSL, which Salesforce identifies as the permission set license providing access to Account Forecasts and related objects.

Salesforce recommends cloning a permission set when additional permissions must be incorporated. A cloned permission set begins with the same license association and enabled permissions as the source, after which the administrator can configure the required field-level access.

For a new custom field, Read access is controlled through field-level security. Current Salesforce documentation explicitly states that field-level security through Object Manager can be set on custom permission sets created for the org. This makes cloning the Manufacturing Account Forecast permission set and extending the clone the appropriate approach.

Options B and D specify the Salesforce license rather than the Manufacturing Account Forecast entitlement. Salesforce states that a permission set associated with a specific license can contain only permissions entitled by that license. Option C does not follow the current custom-permission-set model for extending field-level access.

Therefore, under current Salesforce configuration standards, A is the valid action among the listed options.

Study Guide references/topics: Configure and Build — Account Forecasting; Permission Set Licenses; Manufacturing Account Forecast PSL; Custom Fields; Field-Level Security.