The underlined clause, 'Whenever I walk the dog', is a dependent clause as it is not a complete sentence and is dependent on other independent clause, ' I feel great'.
A dependent clause is an incomplete sentence which is dependent on an independent clause to make a complete meaningful sentence. A dependent clause does not have a literal meaning.
In the sentence, 'Whenever I walk the dog, I feel great', there are two clauses, the first part of the sentence is a dependent clause and the second part is an independent clause, which is completing the sentence.
Therefore, option, B, 'A dependent clause', is correct.
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