I.Choose the Correct Answer 1. A disturbance can be written x b xt b t a y(x,t) (e e e ) 2 2 −( / ) 2 / − = . This disturbance is ( D ) (A) Not a traveling wave. (B) A traveling wave with speed v = a. (C) A traveling wave with speed v = a/b. (D) A traveling wave with speed v = b
一、(在每小题列出的四个备选项中只有一个是符合题目要求的,请将其代码填写在题后的括号内。错选、多选或未选均无分。) 1.根据药物对胎儿的危害,药物可分为哪几类:( ) A ABCDE B ABCDX C ABCD D ABCX 2. 哪类人不属于三种特殊人群范畴:( ) A 老人 B 新生儿 C 幼儿 D 孕妇