他解开婴儿背带上的按扣，把孩子放下来。

He ___unsnapped the baby carrier to put the child down.

她解开背包上的扣子，把水瓶取了出来。

She ___unsnapped the buckle on her backpack to take out the water bottle.

背包的扣子突然松开了，发出啪的一声。

The buckle on the backpack ___came unsnapped suddenly with a click.