21.Database synchronization is in progress.

A. 确保电门在所有面板中设为正确的状态。

B. 确保每个面板中电门指示灯的处于关掉状态。

C. 确保每个面板中的电门设置为关闭状态。

A. 系统接口电路适配已连接系统的物理特征。

B. 系统的电路跳开关符合连接系统的物理特性。

C. 系统电路的物理特点与所连接系统相匹配。

A. 必要时,应使用示意图来指示“流量”,并以尽可能直接的方式说明空气控制、电气、流体动力、燃料和涡轮系统的操作。

B. 必要时,应使用示意图显示“工作流程 ”,简洁明了地显示气源系统、电源系统、液压系统、燃油系统和涡轮系统的运行。

C. 必要时应使用示意图,以表明“流向”,并以尽可能直接的方式说明空气控制、电气、流体动力、燃料和涡轮增压系统的操作。

D. C.必要时应使用示意图,以表明“流向”,并以尽可能直接的方式说明空气控制、电气、流

E. C.必要时应使用示意图,以表明“流向”,并以尽可能直接的方式说明空气控制、电气、流体动力、燃料和涡轮增压系统的操作。

A. 试验结果表明,需要实施故障识别程序。

B. 如果测试没有给出满意的结果,执行故障隔离程序。

C. 如果测试结果不满足,启动故障探测程序。

A. The power plant refers to the overall power package,including engine,air intake,bracket,cowling,nacelle,cowl flaps,cooling baffles,etc.

B. The power plant refers to the overall power package inclusive of engine,air intake,mount,cowling,scoops,cowl flaps,cooling baffles,etc.

C. The power plant refers to the overall power package inclusive of engine,air intake,mount,cowling,nacelle caps,fairing flaps,cooling baffles,etc.

A. 检查开口是否从边角开始出现裂纹。

B. 检查角落位置是否出现开口裂纹。

C. 在拐角处开始检查开口是否有裂纹。

A. Modifications,additions and omissions,a black line should be drawn vertically at the footer outside of the page parallel to the part of the change.

B. Revisions,additions and deletions shall be identified by a vertical black line along the outside of the page opposite only that portion of the printed matter that was changed.

C. Alterations,substitutions and eliminates should be marked with a black slash outside the scope of the page to coincide with the section being changed.

A. During ground speed braking,all the spoiler panels are activated.

B. During ground deceleration,all the spoiler panels are closed.

C. During ground speed stabilizes,most of the pedals are activated.

A. 如燃油面涨到通气油箱高度,则燃油将从通风口中排出。

B. 如燃油水平在通气油箱有充足高度,则燃油将从通风扇中排出。

C. 如燃油油位在通气油箱中足够高,则燃油将从通风戽中排出。

A. Those units and components are used to keep account of data that is unrelated to a particular system.

B. The purpose of those units and components is to obtain values that are independent of a particular system.

C. The function of these units and components is to save the files that have nothing to do with a peculiar system.