Usted is basically the formal way of saying Tú (you).
¿Tenemos fruta? = We have fruit?
¿Tienen fruta? = Do you guys have fruit?(plural)
¿Tiene fruta? = Do you have fruit? (singular)
Since “usted” is singular - the answer is
3. ¿USTED tiene fruta?
If it were to be “ustedes” - the answer would have been
2. ¿Ustedes tienen fruta?
