根据对话内容，选择正确答案。

Linda: Hello, my name is Linda Brown. What's your name?
Tony: I am Tony Smith. Nice to meet you!
Linda: Nice to meet you, too (也)! What is this?
Tony: Oh, it is a photo of my family.
Linda: Is this your mother?
Tony: Yes.
Linda: Is he your father?
Tony: Yes, he is.
Linda: And is the baby (婴儿) your brother?
Tony: Haha, it isn't. It is my sister.

权利和义务都不可能孤立地存在和发展。它们的存在和发展都必须以另一方的存在和发展为条件。它们的一方不存在了，另一方也就不可能存在。