Gabin's hamster eats 30 grams of food a day. Hence the correct option is c.
In the given graph, the horizontal axis represents the number of days, and the vertical axis represents the mass of hamster food in grams. The point (1, 30) on the graph indicates that on day 1, the hamster has consumed 30 grams of food. Therefore, the interpretation is that Gabin's hamster eats 30 grams of food per day.
The value 30 is associated with the daily consumption of the hamster, not the frequency of feeding. It doesn't mean that Gabin feeds his hamster every 30 days; rather, it signifies that, on each day, the hamster consumes 30 grams of food. This understanding is derived from the specific point (1, 30) on the graph, providing a snapshot of the hamster's daily food intake. Hence the correct option is c.