When atoms are touching, how is that communicated in the code?

According to the models that are shown, the individual atoms are represented using single letters. A code is made using the letters to show the relative orientation of the atoms. If the atoms are touching, they are all listed together in a single code. For example, R represents the round atoms while Sq represents the square atoms. If these are touching, the code for them is RSq.

The answer options is d