The correct synonym for ABATE is B: Reduce. The verb "abate" means to become less intense or widespread, or to make something less intense or widespread. It implies a decrease in degree, force, or amount. For instance, a storm might abate, meaning its intensity lessens, or a pain might abate, meaning it becomes less severe.
Let's look at the other options: A: Increase means to become or make greater in size, amount, or degree, which is the direct opposite of abate. C: Expand means to become or make larger or more extensive, also an antonym. D: Multiply means to increase in number or quantity, often by reproduction, or to perform the mathematical operation of multiplication. Therefore, "reduce" is the only option that accurately captures the meaning of "abate," signifying a decrease or lessening of something. Understanding such vocabulary is crucial for precise communication.