After the Mauryan dynasty, the Magadha region was ruled by the Shunga dynasty. Option 1, Haxyan ka dynasty, is incorrect as there is no historical evidence of such a dynasty ruling Magadha. Option 2, Shishunaga dynasty, is incorrect as the Shishunaga dynasty preceded the Mauryan dynasty and not succeeded it. Option 4, Nanda dynasty, is incorrect as it was the ruling dynasty before the Mauryan dynasty. Therefore, the correct answer is option 3, Shunga dynasty. The Shunga dynasty ruled over Magadha from around 185 BCE to 73 BCE, before being overthrown by the Kanvas. They played a significant role in the revival of Hinduism and the traditional Vedic culture after the Mauryan period.