A. Free speech is protected in the US. B. The news media can be very helpful. C. Online reviews can be very powerful. D. Online reviews can lead to legal action.
A. 格里菲斯肺炎双球菌体内转化实验 B. 艾弗里转化因子实验 C. T2噬菌体侵染实验 DNA的X射线衍射图谱实验
A. 其基本组成单位是脱氧核糖核苷酸 B. 四种碱基分别为A T C G C. 空间结构为双螺旋 D. 碱基对排列在内侧构成其基本骨架
A. 对 B. 错
A. 1968 B. 1995 C. 1996 D. 1997