Which phrase could effectively start an additional consideration in an argument?

The phrase "Furthermore" is an effective way to start an additional consideration in an argument because it indicates that the speaker or writer is about to present more information that builds on or adds to the previous points made. It serves to introduce extra details or arguments that reinforce the main idea, showing continuity in the discussion and enhancing the overall strength of the argument.

In contrast, other choices can suggest different relationships between statements. "On the contrary" typically introduces a point that opposes what was previously stated, which may distract from adding further supportive arguments. "Specifically" often narrows down to a detail or example, which doesn’t inherently provide additional support or argumentation but rather elaborates on a point. "Consequently" suggests a cause-and-effect relationship, indicating a result derived from earlier statements, rather than introducing further ideas into the discussion. Therefore, "Furthermore" aptly aligns with the context of expanding upon an argument.