With reference to the scientific progress of ancient India, which of the statements given below are correct?

With reference to forced labour (Vishti) in India during the Gupta period, which one of the following statements is correct?

With reference to the history of India, the terms "kulyavapa" and "dronavapa" denote

From the decline of Guptas until the rise of Harshavardhana in the early seventh century, which of the following kingdoms were holding power in Northern India? 1. The Guptas of Magadha 2. The Paramaras of Malwa 3. The Pushyabhutis of Thanesar 4. The Maukharis of Kanauj 5. The Yadavas of Devagiri 6. The Maitrakas of Valabhi