Why B?

@Valerie you are correct that this is a cause & effect argument. The proposed cause that the author is trying to explain is that "the deforestation rate of this environmentally sensitive zone was significantly lower than in previous years." The proposed cause? According to the Melonian government, this is a result of the millions of dollars spent last year to enforce laws against burning and cutting of the forest. You are also correct that (B) is weakening the Melonian govenrment's claim by pointing out an alternative cause, i.e. it wasn't actually the enforcement of laws against burning and cutting of the forest but rather an abnormally heavy rainfall during the usually dry 6-month annual burning season. So this is alternative cause for the significantly lower deforestation rate, i.e. the abnormally heavy rainfall prevented burning not enforcement of laws against burning. Hope this helps! Please let us know if you have any other questions.

Lol! Can't believe I could not see it myself! For some reason my attention was focused solely on "cutting". Duh! Thank you very much!