Which of the following transitions would best introduce a new idea?

The best choice to introduce a new idea is the option "Furthermore." This transition effectively signals that additional information or a new point will be presented, building upon what has already been discussed. It implies a sense of continuity and expansion, which is ideal for introducing related concepts or additional aspects of a topic.

The other options serve different functions in writing. For instance, "Nevertheless" indicates a contrast or exception to a previously stated idea, making it unsuitable for introducing new concepts. "First" typically signals the beginning of a sequence rather than the introduction of a new idea and is often used when listing points in order. "Consequently" suggests a cause-and-effect relationship, implying that the subsequent idea is a direct result of what preceded it, rather than being a new point altogether. Thus, "Furthermore" is the most appropriate choice for signaling the introduction of a new idea in a coherent manner.