Thanks for the question! So (A) and (B) are actually the complete opposite. (A) is saying that the statement about smaller fires is supporting the contention that the Forestry Department is not doing its job properly if it doesn’t extinguish forest fires as quickly as possible; in other words, it is for that argument. (B) is saying that this statement is used as evidence against the content that the Forestry Department is not doing its job properly if it doesn’t extinguish forest fires as quickly as possible; in other words, it is used to attack that argument.
Hope this helps! Feel free to ask any other questions that you might have.