1 . Some students don’t know ______ (如何平衡学习与玩耍). (根据汉语提示完成句子)

2 . After a while, a group of women came along, ________ a pot of water on her head. One woman ________ and her water pot went crashing to the ground. （根据句意填空）

3 . 在发展与文化遗址保护之间找到恰当的平衡点，并加以保持，这可能是一项巨大的挑战。
______ and ______ the right _________ between progress and the protection of cultural sites can be a big   ______ .