在变频器驱动系统中，电动机的调速控制是通过改变变频器的（）进行的。 A.输出阻值 B

在顾客评价服务质量的五大标准中，（）是指企业对其顾客所给予的关心和个性化的服务。

A.可感知性

B.可靠性

C.移情性

D.保证性

图所示的四种现象中，由于光的折射形成的是[ ]

A． 影子

B． 倒影

C． 水面“折枝”

D． 镜中花

While completing a project a project manager realizes be needs to decrease project costs. After researching his options, he comes up with the following choices. Which choice would DECREASE project costs

A) Change to component A from component B. Component A costs more to purchase but has a lower life cycle cost than B.
B) Change task A to be completed by resource B instead of Resource C, Resource B is a more experienced worker.
C) Move tasks B and H to occur concurrently, and take the risk of a 30% increase in the need for five more resources later.
D) Remove a test from the project plan.

一般来说，投资者应选择增长型的行业和在行业生命周期中处于成长阶段和成熟阶段的行业。（）

简述教师专业发展的主要内容。