Final answer:
a) Rice cereal fortified is the best first solid food for infants due to its digestibility and iron fortification.
Step-by-step explanation:
The best first solid food to introduce to infants is a. rice cereal fortified. This is because rice cereal is gentle on the baby's digestive system, is low in allergens, and is often fortified with essential nutrients like iron.
When introducing solid foods to an infant, it's common practice to start with single-grain cereals like rice cereal before moving on to other foods like strained vegetables, fruits, and meats. The fortification of rice cereal helps overcome the iron deficiency that can occur in infants around 6 months of age.