It was not until she arrived at the classroom she realized she had forgotten her coursebook.

A．and she realized

B．which she realized

C．then she realized

D．that she realized

蒋廷黻说，道光年间的中国人，完全不懂国际公法和国际形势，所以他们争所不当争，放弃所不应当放弃......。文中“争所不当争”是指（）

A、五口通商

B、协定关税

C、治外法权

D、公使驻京