Answer:
D). Conjunction.
Step-by-step explanation:
Conjunction is illustrated as the word which is employed to link two words, clauses or sentences together and describes how the two words or phrases are related to each other. It is exemplified as the part of speech that acts as a bond to unite the two clauses or sentences in co-operation to offer a more complete and coherent thought.
In the given question, the word 'but' functions as coordinating conjunction in the sentence as it joins the two independent clauses 'My dog, Stella, loves to go for walks in good weather' and 'refuses to step outside if it is raining' to offer a more accomplished thought. Thus, option D is the correct answer.