①一切以时间、地点、条件为转移
②必须把树立创新意识作为实践的出发点
③从不显著的质变中坚持适度原则
④把发挥主观能动性和遵循客观规律结合起来
A:①③
B:①④
C:②③
D:②④
在探究“杠杆的平衡条件”实验中.
______ a glass of water in his hand, Mike walked into his bedroom.