AWS Systems Manager is a management service that provides operational insights and control over your AWS infrastructure. A key feature within Systems Manager is Patch Manager, which automates the process of patching managed nodes, including Amazon EC2 instances or on-premises servers. It can be used to apply patches for both operating systems (like Windows Server) and applications. You can define patching baselines, schedule patching windows, and scan instances for compliance, directly addressing the company's requirement for automated patching of its Windows EC2 instances.

B. AWS Organizations is a service for central governance and management of multiple AWS accounts. It does not perform operational tasks like patching individual instances.
C. AWS Control Tower is used to set up and govern a secure, multi-account AWS environment. It orchestrates other services but is not the tool for direct instance patching.
D. Elastic Load Balancing (ELB) distributes incoming application traffic across multiple targets, such as EC2 instances, to ensure high availability and scalability, not for instance management.

1. AWS Systems Manager User Guide: "AWS Systems Manager Patch Manager automates the process of patching managed nodes with both security-related and other types of updates. You can use Patch Manager to apply patches for both operating systems and applications." (Source: AWS Systems Manager User Guide, "AWS Systems Manager Patch Manager", Introduction section).

2. AWS Organizations User Guide: "AWS Organizations is an account management service that enables you to consolidate multiple AWS accounts into an organization that you create and centrally manage." (Source: AWS Organizations User Guide, "What is AWS Organizations?", Introduction section).

3. AWS Control Tower User Guide: "AWS Control Tower provides the easiest way to set up and govern a new, secure, multi-account AWS environment, called a landing zone." (Source: AWS Control Tower User Guide, "What is AWS Control Tower?", Introduction section).

4. Elastic Load Balancing User Guide: "Elastic Load Balancing (ELB) automatically distributes your incoming traffic across multiple targets, such as EC2 instances, containers, and IP addresses, in one or more Availability Zones." (Source: Elastic Load Balancing User Guide, "What is Elastic Load Balancing?", Introduction section).