【单选题】A person pulls a box along the ground at a constant speed. If we consider Earth and the box as our system, what can we say about the net external force on the system?
A.
It is zero because the system is isolated.
B.
It is nonzero because the system is not isolated.
C.
It is zero even though the system is not isolated.
D.
It is nonzero even though the system is isolated.
【单选题】What is the first thing you should consider when thinking about building an international information system?
A.
the state of world politics
B.
look for new technologies that will help you achieve your goals
C.
consider the global environment where your business will operate, and identify the business drivers for your firm and industry
D.
the business challenges you face in the global environment
E.
the different computing and communication standards in the world
【单选题】Consider a system excited by a periodically changing external load. Which one of the following is true?
A.
The amplitude of the displacement response can be reduced if the mass becomes smaller.
B.
The response becomes larger if the excitation frequency is increased.
C.
Severe vibration takes place as the excitation frequency comes close to one of the system’s natural frequencies.
D.
There is nothing one can do to turn down the vibration scale because it is a random function of time.
【单选题】An EFI system can be consider as having subsytems.
【单选题】图示超静定结构,其基本结构如右图所示,则【图片】为:【图片】
【单选题】下列说法不正确的是:
B.
细胞癌变,与细胞内遗传因素有关,许多致癌物质,它改变了细胞核内的物质
C.
动物细胞和植物细胞都有细胞膜、细胞质、细胞核
【多选题】为什么“我”会为母亲卖白菜的决定而哭?
A.
因为那三棵白菜原是准备留着过年包饺子的,在那个极端贫困的家庭,这是一个小孩子最大的盼望。
D.
因为这些白菜是我和母亲亲手种植、侍弄的,我对这些白菜有着深厚的感情。