题目:AIDS has become one of the first killers to human beings. Despite their lack of success so far, scientists have ________ in their research for a cure for AIDS.
A. . suspended
B. . retained
C. . insisted
D. . persevered
答案:评论后可见此内容
推荐使用我们的公众号搜索题目,题目更全,检索更方便。支持语音、图片、文字等多种搜索方式。