It' s Sunday morning. There are many people in the park, some boys are playing basketball. There are some girls under a big tree. They' re singing and dancing. What are those women doing? They are drinking tea. Look at the woman in a blue coat. Who' s she? She' s my mother. She is talking to Edward. Edward is her student. He is a good student. He studies hard . He' s good at all the subjects. And he' s friendly to all his teachers and his friends.
)，会对人体产生一定
危害。该原子中中子数和质子数之差是