新闻中提到了使用drone aircraft（无人驾驶飞机） 的目的是“to collect whale mucus from humpback whales at sea”， 故选C。

【录音原文】
Some scientists have begun using drone aircraft, also known as unmanned aerial vehicles, to collect some of the fluids expelled by whales. Vanessa Pirotta is a researcher with Macquarie University in Sydney, Australia. She told the Reuters news agency that a drone has been used for the first time to collect whale mucus from humpback whales at sea. She believes that drones could help improve scientists understanding of whales around the world.