I was able to get the sense of the example, but when digging deeper, a few inaccuracies were troublesome.
We can keep the picture, get rid of it, or use a simple version:
```
    ?                         ?
   / \                       /|\
 (A)  B   Removal of A      / | \
 / \          ===>         /  |  \
C  (D)                    C  (D)  B
 <-                        <-   ->
```