Final answer:
Signal words should be used when introducing evidence in a cause-and-effect essay
Step-by-step explanation:
The most important time to use signal words in a cause-and-effect essay is when introducing evidence. Signal words are used to indicate a cause-and-effect relationship between events or ideas. By using signal words, such as 'because,' 'therefore,' or 'as a result,' the writer can clearly show the connection between the cause and the effect.
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