New foods should be introduced to the infant at intervals of

The correct answer is C (5 to 7 days). Introducing new foods to infants at intervals of 5 to 7 days allows for proper observation of any potential allergic reactions or adverse effects. This timeframe helps in identifying specific food sensitivities and adjusting the diet accordingly. Option A (1 day) is too short for monitoring reactions. Option B (8 to 10 days) is slightly longer than necessary, potentially delaying the introduction of important nutrients. Option D (2 to 3 days) is shorter and may not provide sufficient time to detect reactions.