In relation to Amazon Simple Workflow Service (Amazon SWF),what is an “Activity Worker”?

A.
An individual task undertaken by a workflow

B.
The automation of a business process

C.
A piece of software that implements tasks

D.
All answers listed are correct

Explanation:
In relation to Amazon Simple Workflow Service (Amazon SWF), an activity worker is a program that receives activity
tasks, performs them, and provides results back. Which translates to a piece of software that implements tasks.
http://docs.aws.amazon.com/amazonswf/latest/developerguide/swf-dg-develop-activity.html