How do I make an <a> tag the size of it's parent <li> tag?

[ydubuoprlb]

I have the same question that this guy has asked here: How do I make an <a> tag the size of it's parent <li> tag for larger clickable region?However I would like these LI items like an inline menu, so I don't want them to list under each other. How is it aciveable?