许多科学家认为在原始大气中，不含有的物质是[ ] A．甲烷 B．氢 C．水蒸气

最早的标点符号产生于（），18世纪，英语标点系统成型，19世纪，标点传入中国，1919年2月，胡适的《中国哲学史大纲》出版，书中第一次使用了新式标点。

When Helen saw his tutor nod _____ to her, she felt greatly ______ and was convinced that she would be __________ she had been dreaming of .

A．encouragingly; encouraging; as a successful person as

B．astonishingly; encouraged; as successful a person as

C．encouragingly; encouraged; as successful a person as

D．astonishingly; encouraging; as a successful person as

通过募集设立方式设立股份有限公司，发起人认购的股份不得少于公司股份总数的( )。

A．25%

B．30%

C．35%

D．40%

《招标投标法》规定，招标人和中标人应当自中标通知书发出之日起( )日内，按照招标文件和中标人的投标文件订立书面合同。

A．5
B．10
C．20
D．30

会导致咀嚼无力的是

A．基托边缘过长或过锐
B．基托变形
C．基托写黏膜不密合
D．人工后牙覆盖过小
E．垂直距离过低