He left the room, _________.( ) A: his nose bled, his hands shake B: . his nose bled, his hands shaking C: his nose bleeding, his hands shake D: his nose bleeding, his hands shaking

路灯一般使用的灯是（） A: A高压钠灯 B: BLED灯 C: C荧光灯 D: D卤素灯

光纤的主要作用是传输信号，常用产生光信号的光源有两种，即（）。 A: A发光二极管和半导体激光管 B: BLED管和晶体二极管 C: CILD管和激光二极管 D: D激光管和半导体晶体管

When I arrived there, the old man [u]       [/u] with a knife, [u] [/u] a lot. 未知类型：{'label': 'questionDesc', 'content': '请选择正确答案。', 'isMemberControl': 0, 'type': 181} A: was wounded , bleeding B: had wounded, bled C: wounded, to bleed D: has been wounded, bleed

光通信领域中，LD和LED相比，主要区别在于（） A: ALD发出的是激光，LED是荧光 B: BLED的谱线带宽较宽，调制效率低 C: CLD一般适用于大容量、长距离的传输系统 D: DLED成本低，适用于短距离、小容量的传输系统