Select certain number child or children selector withing parent. css

Is there a way to select a certain number of child selectors? For example

<div class="parent">
  <div class="child-a">abc</div>
  <div class="child-b">def</div>
  <div class="child-c">ghi</div>
  <div class="child-d">jkl</div>
  <div class="child-e">m开发者_Python百科no</div>
  <div class="child-f">pqr</div>
  <div class="child-g">stu</div>
</div>

How can I select just .child-a, .child-b, .child-c ?

Or just select .child-d .child-e, .child-f ?

Can it be done with :nth-child pseudo-classes like

  div.parent div:nth-child(1,2,3) { margin: 15px 0 0 0; display:inline }
  div.parent div:nth-child(4,5,6) { margin: 30px 0 0 0; display:inline }

? something like that?

Well, if the divs have those classes, you can simply list them:

.child-a, .child-b, .child-c

If you want to do it with nth-child, you must list them like this:

.parent :nth-child(1), .parent :nth-child(2), .parent :nth-child(3)