the scenario is:

C: Win 10
D: Data
E: Win 10 for experiments

C: can see D: but cannot see E:
E: cannot see C: and D:

I want to apply BitLocker only for C: and D: while E: can remain without it.

Is that possible? Both C: and E: has quick boot disabled.

Also, is Bitlocker related to a OS or to hard disks? I mean, I can even use Bitlocker for all my OSs in the system or Bitlocker is related to the single OS?