Answer:
Personification is the figure of speech in the sentence.
Explanation:
"Lofty mountains that pierce the clouds and reach to dizzying heights may appear to us humans as coldly majestic, lonely, even forbidding.
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Mountains are not creatures that have feelings as they are not living things; thus, using the metaphor "pierce the clouds", describing them as "coldly majestic" and "lonely lends to them characteristics of human beings, which is what personification is all about.
