Contact Form 7 Display Block for one group of list items

I am aware I can use the following code

span.wpcf7-list-item { display: block; }

But this would effect every list item on every form.

How would I create a class that I can add to the checkbox field that would only effect that group of checkboxes?

I tried using the following code:

.check-block-list-item {
  display:block;
}

The form would look like [checkbox my-name class:check-block "option 1" "option 2" ]