Solution:The four-way phonation contrast-unvoiced unaspirated, unvoiced aspirated, voiced unaspirated, and voiced aspirated-is a hallmark of Indo-Aryan phonological systems. Languages such as Hindi, Bengali, Marathi, Gujarati, and Punjabi display this contrast across stop consonants. This feature stems from ancient Indo-Aryan (Sanskrit) and continues to be a prominent characteristic of modern Indo-Aryan languages, unlike Dravidian, Austro-Asiatic, or Tibeto-Burman languages, which typically lack this full four-way distinction.