选择题：Much research _______ into the possible causes of

题目内容：

Much research _______ into the possible causes of the disease in the past few years.　
(A) has been done
(B) was done
(C) have been done
(D) were done

参考答案：

In my opinion, high-IQ students are usually intell

In my opinion, high-IQ students are usually intellectually curious and very good

I’ve got a big coffee ____ on the front of my dress.　(A)pore(B)patch(C)sta

Before going to bed, she _______ that the door was locked.　(A)insured herself

劳动力流动成为人力资本投资方式之一的原因在于（）(A)劳动力流动费用直接形成人力资本存量(B)劳动力流动费用直接增加人力资本存量(C)劳动力流动费

15.在劳动过程中，防止人员伤亡事故和职业病发生的主要措施是(A)加强福利待遇(B)改善劳动条件(C)提高员工自我保护意识(D)保障劳动者权益