Explanation
To support the requirements with the minimum amount of effort, three platform security features that are required are criteria-based sharing rules, role hierarchy, and permission sets. Criteria-based sharing rules can be used to share all accounts with the custom field "Kay Customer" to all senior account managers based on a filter condition. Role hierarchy can be used to grant access to accounts that users or their subordinates own based on the ownership and role level. Permission sets can be used to grant view and edit access to the custom field that contains sensitive information to the three designated users, regardless of their user groups or profiles

Explanation
Implementing a third-party proxy server is the best technology to achieve the requirement of accessing on-premise information from Salesforce. A proxy server acts as an intermediary between Salesforce and the on-premise database, and it can handle authentication, encryption, and data transformation. Option A is incorrect, as tokenization is a technique to replace sensitive data with tokens, not to access on-premise data.
Option B is incorrect, as it does not specify how Salesforce can connect to the on-premise database. Option D is incorrect, as Salesforce Shield is a set of tools to enhance data security and compliance in Salesforce, not to access external data sources.

Explanation
To implement Apex managed sharing, a Salesforce Developer should consider using the with Sharing keyword and the runAs system method. The with Sharing keyword ensures that the Apex class respects the record visibility rules of the current user context, which can help prevent unauthorized access to records that are not shared with the user1. The runAs system method allows testing the code as different users with different profiles and permissions, which can help verify that the sharing logic is working as expected2.

Explanation
Programmatic sharing is the best option to share accounts automatically based on a lookup field, as it allows for more flexibility and scalability than manual sharing, account teams, or criteria-based sharing. Manual sharing is not automatic and requires user intervention. Account teams are not suitable for large numbers of users and accounts. Criteria-based sharing does not support lookup fields as criteria