The word "l'infant" is a contraction of the words "le enfant" (meaning the child. Because enfant starts with a vowel, it is grammatically incorrect to say le enfant (they do this so that the language sounds better), you must say l'enfant (the child).
The instructions say to type the French that i hear, not to type the English translation. So I type, L'enfant a une livre, and it keeps telling that's incorrect, it should be the child has a book. What am I missing??