脑血管病常见病因哪项不正确（） A.脑血管病最常见原因是动脉粥样硬化 B.先天性动脉

下列关于计算机病毒的叙述错误的是( )

A．计算机病毒只能通过网络传播
B．计算机病毒是一种有害程序
C．计算机病毒具有隐蔽性的特点
D．计算机病毒是一种能够自我复制的一组计算机指令和程序代码

我某出口公司与非洲某商成交货物一批，来证规定9月装运，但计价货币与合同规定不符，加上备货不及，直至9月对方来电催装时，我方才向对方提出按合同货币改证，同时要求展延装运期。次日非商复电“证已改妥”，我方据此将货发运，但信用证修改书迟迟未到，致使结汇单据寄达开证行时被拒付。我方为及时收回货款，避免在进口地的仓储费用支出，接受了进口商改按D/P·T/R提货的要求，终因进口人未能如约付款使我方蒙受重大损失。 试就我方在这笔交易的处理过程进行评论，找出我公司应吸取的经验教训。

下列气体灭火系统分类中，按系统的结构特点进行分类的是（）。

A.二氧化碳灭火系统，七氟丙烷灭火系统，惰性灭火系统和气溶胶灭火系统

B.管网灭火系统和预支灭火系统

C.全淹没灭火系统和局部应用灭火系统

D.自压式气体灭火系统，内储压式气体灭火系统和外储压式气体灭火系统

Virtual reality (or VR (1) ) is kind of a buzzword these days in computer graphics.VR is artificial reality created by a computer that is so enveloping that it is perceived by the mind as being truly real.VR exists in many (2) .A traditional view of virtual reality uses headsets and data gloves.The headset serves as the eyes and ears to your virtual world,projecting sights and sounds generated by the computer.The data glove becomes your hand,enabling you to interact with this (3) world.As you move your head around,the computer will track your motion and display the right image.VR is the most demanding (4) for computer graphics,requiring hardware and software capable of supporting realtime 3D (5) .

A．App

B．apply

C．application

D．appliance

运送哪些货物不核收运费？