To answer your question, clearly the answer is b. That is exactly the double standard as stated.
What I'm really trying to get at is that no one should be staying home full time while the other is at work all day.
Careers are a very personal thing. Having a child shouldn't be thought of as something you do for yourself. You are doing it for the child and the world. It is important to raise them right, but not at the cost of your future. With two parents, it shouldn't be that difficult to split the time across both.
That may sound wrong, but in reality, it takes a village to raise a child. Why should one person sacrifice the rest of their life?