In a polytropic process
(a) $$\frac{T_1}{T_2} = \left(\frac{V_2}{V_1}\right)^{n - \frac{1}{n}} = \left(\frac{p_1}{p_2}\right)^{n - 1}$$
(b) $$\frac{T_1}{T_2} = \left(\frac{V_2}{V_1}\right)^{n - 1} = \left(\frac{p_1}{p_2}\right)^{n}$$
(c) $$\frac{T_1}{T_2} = \left(\frac{V_2}{V_1}\right)^{n - 1} = \left(\frac{p_2}{p_1}\right)^{n - 1}$$
(d) $$\frac{T_1}{T_2} = \left(\frac{V_2}{V_1}\right)^{n - 1} = \left(\frac{p_2}{p_1}\right)^{n - \frac{1}{n}}$$