According to Chapter 38, how does the prescribed form of virtue or duty change through the different cosmic ages, and what is considered supreme in the current age?

Chapter 38 references the scriptures of human duty to explain how the primary means of spiritual progress changes with the ages. It states that Penance was the key in the Krita age, Knowledge in the Treta age, and Sacrifice in the Dvapara age. For the current era, the Kali age, Charity is presented as the most effective path. Within the realm of charity, this chapter explicitly declares that the regular practice of food donation (Annadan) is the foremost among all deeds and the highest secret for quenching hunger, establishing it as the supreme virtue for our time.