Which of the following holds good in all natural processes?

• A. The Doppler Effect
• B. Newton‚Äö√Ñ√∂‚àö√ë‚àö¬•s law of gravitation
• C. Electromagnetic law
• D. Lenz‚Äö√Ñ√∂‚àö√ë‚àö¬•s law