明朝医药学家李时珍所著的一部具有总结性的药物学著作是（    ）

现在车上有____人。把你的想法与同伴说一说。

    One day, Tom is swimming in a river. He doesn't swim well and will be drown(淹死). He calls out loud for help. A man is just passing by. He doesn't help the boy, but stands by and says to him. “It is dangerous to swim in the river.” “Oh, yes sir,” cries the boy, “ Please save me and scold (责备)me later.”

    Counsel without help is useless.