NO.7信号单元中，SIF信息字段是（）信号单元所特有的字段。A.LSSU B.FI

把0.05 mol NaOH固体分别加入到100 mL下列液体中，溶液的导电能力变化最小的是

A．自来水

B．0.5 mol·L^－1盐酸

C．0.5 mol·L^－1CH₃COOH溶液

D．0.5 mol·L^－1KCl溶液

电磁波在真空中传播的速度是      m/s。

Teams are required for most engineering projects. Although some small hardware or software products can be developed by individuals, the scale and complexity of modern systems is such, and the demand for short schedules so great, that it is no longer (1) for one person to do most engineering jobs. Systems development is a team (2) ,and the effectiveness of the team largely determines the (3) of the engineering. Development teams often behave much like baseball or basketball teams. Even though they may have multiple specialties, all the members work toward (4)．However, on systems maintenance and enhancement teams, the engineers often work relatively independently, much like wrestling and track teams. A team is (5) just a group of people who happen to work together. Teamwork takes practice and it involves special skills. Teams require common processes; they need agreed-upon goals; and they need effective guidance and leadership. The methods for guiding and leading such teams are well known, but they are not obvious.

空白（4）处应选择（）

A.multipleobjectives

B.differentobjectives

C.asingleobjective

D.independentobjectives

下列关于传染病流行病学特征的描述，错误的是（）

A.霍乱是外来性传染病

B.发病率高于一般水平为流行

C.流行范围超过国界或洲界时为大流行

D.短时间内病例集中发生为暴发

E.不同人群中的分布不属于流行病学特征

某公司2006年赊销收入为300000元，销售毛利率为30%，在2007年保持不变。2007年该公司拟改变原有信用政策，有甲、乙两个方案可供选择，资料如下(应收账款机会成本为10%)：

项　　目	甲方案	乙方案
信用期限	30天	40天
现金折扣	无	2/10,n/40
销售收入	360000	420000
平均收现期	45天	25天
取得现金折扣的%	0	50％
平均坏账损失率	6%	3％

要求：(1)计算甲、乙方案新增毛利润；
(2)计算甲、乙方案的机会成本；
(3)计算甲、乙方案的坏账损失；
(4)计算乙方案的现金折扣；
(5)计算甲、乙方案新增加的净利润；
(6)分析公司应采取哪种信用政策。