Final answer:
The molar conductance at infinite dilution cannot be determined by extrapolating the plot between molar conductance (Δm) and time. Conductance relates to ion concentration and not time, and molarity is temperature-dependent, whereas molality and mole fraction are not. Therefore, the correct option is C.
Step-by-step explanation:
The molar conductance at infinite dilution is determined by extrapolating the plot between molar conductance (Δm) and the square root of concentration (√(concentration)). The correct answer to the question 'Molar conductance at infinite dilution cannot be determined by extrapolating the plot between Δm versus what?' is Time (c). This is because molar conductance relates to the conductivity of ions in a solution, which depends on the concentration of ions rather than time.
Molarity can be affected by temperature due to the density changes of a solution, which leads to the contraction/expansion of the solution. Therefore, mole-based concentration units not dependent on temperature, like molality and mole fraction, are more appropriate for colligative property calculations.