I have this D3 code which creates my x axis:

```
svg.append("g")
  .attr("class", "x axis")
  .call(xAxis)

```

How do I select my x axis in my css file? I have:

```
.axis line {
  fill: none;
  stroke: black;
  shape-rendering: crispEdges;
}

```

But this would apply to all my axes (both x axis and y axis). How do I select only x axis? I know css selectors can be cascaded, but I'm not sure exactly how to do that...