ANS:B - < 1

In a single-effect evaporator, the economy is typically less than 1. The economy of an evaporator refers to the ratio of the amount of water vaporized to the amount of steam consumed. Since some energy is lost in the process due to heat losses and inefficiencies, the amount of water vaporized is generally less than the amount of steam consumed. Therefore, the economy is less than 1. So, the correct answer is: "< 1"