vault – n. a locked room where money or valuable things are kept

sample(s) – n. a small amount of something that gives you information about the thing it was taken from

varieties – n. particular kinds of people or things

underground – adj. located or occurring below the surface of the earth

tunnel – n. a passage that goes under the ground or through a hill

construction – n. the act or process of building something

unit(s) – n. a machine or part of a machine or system that has a particular use

safeguard – v. to make someone or something safe or secure

crucial – adj. extremely important

insurance – n. protection from bad things that may happen in the future
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