当婴儿开始大声哭闹时，母亲轻轻哼唱安抚他。

The mother gently ___hummed the baby when he started to cry loudly.

猫咪舒服地蜷缩在毯子里，发出轻柔的咕噜声。

The cat curled up in the blanket and ___purred contentedly.