A：是非金属元素
B：是稀有气体元素
C：是金属元素
D：无法确认为哪一类元素
化学是一门自然科学，研究和发展化学科学的基础是（ ）
____ He's my brother.
____ Who's that boy?
____ Yes, she is.
____ Is she your mother?
____ No, he isn't. He's my teacher.
____ Is he your father?
