渐变型多模光纤
参考答案：
光线以正弦形状传播，带宽可达1-2GHz.km，多用于一些速率不太高的局域网。
American women usually identify their best friends as someone____they can talk frequently. [ ]
A. who
B. as
C. about which
D. with whom
男性，32岁。出现血尿、少尿、水肿、高血压2周，肾功能急剧恶化。B超双肾增大，肾活检可见70%肾小球的肾小囊中有大新月体形成（）.
A.IgA肾病
B.原发性肾病综合征
C.紫癜性肾炎
D.急进性肾炎
E.狼疮性肾炎
