1. What will Sonya's family do this weekend?
2. Her family will plant potatoes.
3. She will plant potatoes with her family.
4. They will plant potatoes.
5. It will plant potoes.
[#1 is the question, and the others are possible answers to the question. Which naswer is incorrect?]
#5 is incorrect. "It" cannot refer to a family. #2 is correct but unnecessarily wordy, because we already know it's about her family, so "they" is enough. #3 is grammatically correct, but doesn't directly answer the question.
To sum up, all are correct except #5, but #4 is the best answer