题目

鲨鱼是世界上惟一不患癌症的动物，科学研究表明，鲨鱼体内含有一种角鲨烯,具有抗癌性。已知鲨烯分子含有30个C原子及6个C=C且不含环状结构,则其分子式为                                   A．C30H48        B．C30H50       C． C30H60        D．C30H62 答案：BAs we grow up, we get better at knowing ______ we are feeling and why.A．what B．how C．that D．whether