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【单选题】
嵌入式系统中硬件层主要包含了嵌入式系统重要的硬件设备： 、存储器（SDRAM、ROM等）、设备I/O接口等。A.
嵌入式处理器
B.
嵌入式控制器
C.
单片机
D.
集成芯片
拍照语音搜题，微信中搜索"皮皮学"使用
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知识点：
皮皮学刷刷变学霸
举一反三
【单选题】Questions 11 to 15 are based on the following passage: Today air travel is very common, but the first flights were very different from today. When air travel began in the 1920s, it was very expensive...
A.
Because it was too expensive.
B.
Because it was too uncomfortable.
C.
Because it was too dangerous.
D.
Because it was too noisy.