光纤的损耗因素主要有本征损耗、（）和附加损耗等。
A.制造损耗
B.连接损耗
C.耦合损耗
D.散射损耗
参考答案：A, B, C, D
--- There is little water left in the bottle, ______?
--- No, we need to buy some more before we run out of it.
A．is there
B．isn’t there
C．is it
D．isn’t it
筋瘤相当于西医的（）
A.脂肪瘤
B.静脉曲张
C.粉刺瘤
D.血管瘤
E.纤维瘤
