紫外可见分光光度法的单波长法作含量测定时，通常选择（）为测定波长，且控制供试品的吸收度读数在（）之间。
参考答案：最大吸收波长；0.3~0.7
线路允许速度vmax≤120km/h，钢轨硬弯大于（）mm时，应及时处理。
A、0.3
B、0.5
C、1
D、2
一 The woman biologist stayed in Africa studying wildlife for 13 years before she returned to her country.
— Oh, dear! She _____ a lot of difficulties.[ ]
A. may go through
B. might go through
C. must have gone through
D. ought to have gone through
