The word, ‘poachers’ is a noun which refers to people who catch and kill animals illegally. It is mentioned in the sentence that they were arrested for illegally hunting the bears. Hence, 'poachers' is the most appropriate noun to fill the blank and option A is correct.
Option B: The word, ‘rangers’ refer to keepers of a park or forest. They also protect animals.
Option C: Soldiers serve in the army and protect the nation.
Neither rangers nor soldiers illegally hunt animals. Hence, both these words are not appropriate answers and options B and C are wrong.
Option D is incorrect because the word ‘roachers’ doesn’t exist. It carries no meaning.