Every time you put on a different pair of shoes, your interaction with the ground changes slightly, thus you stride differently.
每次你穿不同的一双鞋，你与地面的相互作用会产生略微的变化，因此你的步幅是不同的。
2
In the earlier study of SLA, the main focus was on whether pair or group interaction could provide each member with Comprehensible Input which has been claimed to be a crucial element in SLA.