边际产品转换率（Marginal rate of product transformation）
参考答案：边际产品转换率是指生产可能性曲线斜率的负数。
Not all events in history are as_______ as this. [ ]
A. terribly
B. more terrible
C. the most terrible
D. terrible
信使核糖核酸（mRNA, messenger ribonucleic acid）
