A. Because you choose to.
Choosing to work means taking action in the world, which is where you can stop looking for a cause outside yourself. How did you choose, you can still ask. But you choose to work because you choose to work. It's because of this that you can say you have a good work ethic. A choice is something that you take responsibility for. Not your parents, or your work ethic, or the way you were raised.
For you to have any kind of real agency rather than being the product of cause and effect beyond any control of yours would upend both logic and physics (in other words: free will is nothing but an illusion).
Free will is no more an illusion than the qualia of red. If what you think is outside your control, then who is the "you" that is not in control? Where is it?
If you can't choose to swap the color red to blue, then what makes you think you have any other choice with other things in your mind?