1. It is not easy to disprove the existence of aliens as there is still a lack of concrete evidence. (证明外星人存在是并不容易的,因为仍然缺乏确凿的证据。)
2. The scientist conducted numerous experiments to disprove the hypothesis and ultimately succeeded in refuting it. (科学家进行了多次实验来证伪这个假设,并最终成功地推翻了它。)