皇上的（）宝剑，具有先斩后奏的权力？
参考答案：尚方宝剑
要使凸透镜得到实像，物距必须______1倍焦距，而要得到虚像，物距就要______1倍焦距．
Silk（）one of the primary goods traded along the Silk Road by about 100 BC.
A. had become
B. reject
C. control
D. abandon
