A metaphor is a figure of speech which describes an object or action that isn’t literal in its sense, but it helps in creating a comparison to explain an idea. It states the one thing to be another because they are the same in characteristics.
In the above instance, the sequoias are compared to the building being the nature’s “architecture”. Hence the sentence which uses metaphor to the strengthen the topic sentence is A) The towering giants can grow over 200 feet tall.
