Correct option is C
The earliest capital of Magadha was Girivraj, also known as Rajagriha (modern-day Rajgir in Bihar).
Girivraj was the capital during the time of the Haryanka dynasty, especially under kings like Bimbisara.
It was a fortified city, surrounded by five hills, making it naturally secure.
Later, the capital was shifted to Pataliputra by Udayin (Bimbisara's successor's son) due to its strategic location near the Ganges.
Additional Knowledge:
Pataliputra: Became the capital later under Udayin and remained the capital during the Maurya and Gupta periods.
Vaishali: Capital of the Lichchhavi republic, not of Magadha.
Champa: Capital of Anga, not Magadha.