A. Your daughter has no doubt already noticed that there's no father in her family. She probably spends time with friends and cousins who have dads around, and happy little mommy-daddy families are all over children's TV, books, movies, and music. So start laying the groundwork now; plant seeds for how you want her to think about her family.
Luckily, at her age she's probably wondering where a daddy is, not about the particular circumstances that led to her father's not being around. So don't launch into an emotional rant on why that man is not there for her. Instead, help her understand that there are all different kinds of families -- two-parent ones, ones headed by single moms or single dads, still others where grandparents are raising the kids -- and that what's most important in a family is love. Tell her that she has a mom who loves her madly and an extended family that loves her, too. See if you can surround her with positive male role models -- grandpa, uncles, cousins, platonic male friends -- who will show her by example that the world is full of men who are capable of loving, respecting, and protecting her.
Later, around age 5, she'll want to know more about her father and why he's not in her life, and answering her will be complicated and challenging. But it's the much, much simpler answers you give now that will prepare both of you for that day.