列式计算 （1）320的16倍是多少？ （2）960是16的多少倍？ （3）一个

扫描仪是一款常见的输入设备。

硝酸酯类药物舒张血管的作用机制是

A．阻断β受体

B．直接作用于血管平滑肌

C．促进前列环素的生成

D．释放一氧化氮

E．阻滞Ca2+通道

资料和档案的划分，可以直接以其物质形态或具体内容作为标准。

Tidiness

Tidiness means keeping things out of sight and yet available when wanted. It implies that there is a (1) for everything and that each thing used finds its way (2) to its place by a continuos process, not by a spasmodic (3) . The process depends, however, upon the drawer, cupboard and storage (4) being provided, for lack of which one things may literally have (5) place to go. Like the perambulator and trolley, the luggage and the golfclubs (6) be homeless. The same may be true of the deck-chairs (7) the bulkier plastic toys. As there is no place for them, it is no (8) telling people to put them away. The architect who thus economises on (9) space is apt to claim that a good-sized sitting-room is (10) result. What advantage is there in that, however, (11) half the living-room has to be used for storage The aesthetic (12) depends, in turn, upon storage space. (13) it may be true that no house ever had cupboards enough, (14) are some houses which have practically no cupboards (15) all. In these our choice must lie between chronic (16) and ruthless destruction. That is not to say, however, (17) cupboard space will itself create tidiness. Some people (18) happier, it would seem, in chaos. There is the question, furthermore, (19) the cupboards themselves are tidy. That (20) has been swept out of sight is no proof, in itself, that everything can be found.

逻辑无环流可逆调速系统中，当转矩极性信号改变极性时，并有（）时，逻辑才允许进行切换。

A、零电流信号

B、零电压信号

C、零给定信号

D、零转速信号