Radiative transfer modelings of [C I](1–0)/CO(2–1) and [C I](1–0)/¹³CO(2–1) ratios (T_B). The panels indicate the three cases of different n_H2. All model calculations assume a constant [¹²CO]/[¹³CO] = 40. In each panel, there are three groups of ﹩{N}_{{{\rm{C}}}^{0}}/{N}_{\mathrm{CO}}﹩ (1, 3, and 10, shown in blue, green, and red, respectively), where different line tracks indicate different N_CO/ΔV: dotted = 3 × 10¹⁶, solid = 1 × 10¹⁷, and dashed = 3 × 10¹⁷ cm⁻² (km s⁻¹)⁻¹. In each track, points indicate the five cases of T_kin (50, 100, 200, 300, and 500 K) with monotonically decreasing the [C I](1–0)/¹³CO(2–1) ratio with higher T_kin in the case of n_H2 = 10³ cm⁻³ or, conversely, monotonically increasing the [C I](1–0)/¹³CO(2–1) ratio with higher T_kin in the remaining cases; we mark the lowest T_kin = 50 K cases with filled symbols.