"A dog is eating bread."
Translation:כלבה אוכלת לחם.
@Botinok: The exercise at the top of this page is to translate from the English "A dog is eating bread" into Hebrew. The English sentence does not specify the dog's gender, so either gender could be OK. However, the standard translation to Hebrew would be masculine, "כלב אוכל לחם", when gender is unknown or unspecified.
We could only wish that the course creators would explain why a preferred answer deviates from what the course teaches. Otherwise, they create the unnecessary confusion that you experienced.
DL gives you "typo" credit only for a 1-letter error that doesn't create another real and incorrect word.
just as in English, we can't arbitrarily change spelling and expect the word to have the same meaning, even if it sounds the same. Examples: bread and bred; site and cite. In your error, the words don't mean or sound the same: "לֶחֶם" is lékhem; "לָכֶם" is lakhém.
even native speakers ( of both languages, for that matter) make errors in spelling, grammar, and pronunciation. As learners, we are guaranteed to make mistakes, but if the meaning is clear from context, then it might be okay in casual correspondence and conversation.