问题补充：
Which of the following sentences doesn’t contain(包含) an object clause（宾语从句）?
A. Many people believe robots will do most of our work.
B. Scientists should be able to develop plants that grow on Mars.
C. People think that humans on Mars have to wear special boots to make themselves heavier.
D. We all know the next Olympic Games will be held in Beijing.
答案：
A. Many people believe robots will do most of our work.
(答案→)B. Scientists should be able to develop plants that grow on Mars.
C. People think that humans on Mars have to wear special boots to make themselves heavier.
D. We all know the next Olympic Games will be held in Beijing.
解析：根据各个选择项可知B不是宾语从句，它只是个简单句。A和D是that引导的宾语从句，其中that给省略了；C也是that引导的宾语从句。
