发射和接收电磁波的天线有各种各样的，如 _________ 天线、 ______

21世纪全球的平均气温将上升大约4-6摄氏度，是20世纪气温升高的近多少倍

A.3-6倍 

B.4-8倍 

C.5-10倍 

D.2-5倍

关于摩擦的说法，正确的是（　　）

A．一切摩擦都是有害无益的，应尽量减小摩擦

B．摩擦有利、有害，应利用它有益的一面、减小有害一面的影响

C．改变接触面大小，将改变摩擦力的大小

D．滚动摩擦是有用摩擦，所以都是用滚动来代替滑动

为了防止地面汇水倒坡，厨房间地面应比走廊及其他室内地面低（）。

A、20mm

B、30mm

C、25mm

D、10mm

The (1) is a general description of the architecture of a workflow management system used by the WFMC, in which the main components and the associated interfaces are summarized. The workflow enactment service is the heart of a workflow system which consists of several (2) . In a workflow system, a process is specified using the process definition tool. Usually, processes are defined in terms of a (3) , which consists of (4) indicated using a circle, and (5) shown as a rectangle. These two components can be linked by means of a directed arc.

3（）

A．PERT diagram

B．Network Diagram

C．Petri Net

D．Gantt chart

会计年度自公历1月1日起至12月31日止，12月31日为年终决算日，如遇该日为节假日，则下一工作日为决算日。