What is the hierarchy of the process at the receiving end of the cut-back technique?

• A. Photodiode ‚Äö√Ñ√∂‚àö√ë‚àö¬® photo-detector ‚Äö√Ñ√∂‚àö√ë‚àö¬® lock-in amplifier
• B. Photodiode ‚Äö√Ñ√∂‚àö√ë‚àö¬® lock-in amplifier
• C. Photodiode ‚Äö√Ñ√∂‚àö√ë‚àö¬® photo-detector ‚Äö√Ñ√∂‚àö√ë‚àö¬® Attenuator
• D. Photo-detector ‚Äö√Ñ√∂‚àö√ë‚àö¬® lock-in amplifier ‚Äö√Ñ√∂‚àö√ë‚àö¬® receiver