ANS:B - 1-1.3

The amount of steam required for evaporation in a single effect evaporator depends on various factors such as the initial concentration of the solution, desired concentration of the final product, and operating conditions. However, as a general guideline, the evaporation of 1 kg of water typically requires about 1-1.3 kg of steam in a single effect evaporator. Therefore, the correct option is: 1-1.3