The expression for refractivity in terms of the Pressure and temperature coefficient is given by ____________

• A. \(\frac{77.6}{T}P+4810 \frac{e}{T} \)
• B. \(\frac{77.6}{P}T+4810 \frac{e}{T} \)
• C. \(\frac{77.6}{P}T+4810 \frac{T}{e} \)
• D. \(\frac{77.6}{T}P+4810 \frac{T}{e} \)