The clause is “who enjoy the adventure of hitchhiking” which is an essential dependent clause because it gives important information about people. It also is an adjective clause modifying/describing people and answers the question “which?” ; in this case, which people? (those) who enjoy the adventure of hitchhiking. If you were to omit the clause, then the sentence wouldn’t make sense: “Only people should risk running out of gas.” As you can see, adding the clause “who enjoy the adventure of hitchhiking” is essential to the understanding of the sentence. I hope this helps you. I’m a high school English Teacher.

The clause is “who enjoy the adventure of hitch-hiking.” The clause in this sentence is right behind what it modifies or describes– the people. The purpose of the clause is to give the reader more information about the subject of the sentence. This would be an adjective clause because it helps describe the subject.

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It helps to know which clause you are talking about, whether it is the main (or independent) clause or the subordinate clause that modifies the subject in the main clause.