Indonesian forest fire in 1997 was caused by

1. The question asks for the cause of the Indonesian forest fire in 1997. 2. Large-scale forest fires occurred in Indonesia, particularly in Kalimantan and Sumatra, during 1997-1998, causing significant haze across Southeast Asia. 3. While El Nino effects exacerbated drought conditions, making forests more susceptible to fire, the primary cause of the fires was widespread slash-and-burn practices used for land clearing, primarily for agriculture (like palm oil plantations) and logging. 4. These human activities were the ignition source, although the severe drought linked to El Nino allowed the fires to spread uncontrollably. 5. Options A (greenhouse effect) and B (ozone depletion) are broader environmental issues not the direct cause. Option C (El Nino effects) was a major contributing factor (drought) but not the sole or initiating cause (which was human activity). 6. Since the direct cause (slash-and-burn) isn't listed, and El Nino was a critical enabling condition, the situation is nuanced. However, if the question seeks the 'trigger', it was human action. If it seeks the 'condition', El Nino is relevant. Given the provided answer is (D) None of the above, it implies that none of the specific options (A, B, C) were considered the primary cause by the source.