【单选题】A large horizontal axis wind turbine operating at the design wind speed will take about half the energy from the wind. Why can it not take all the energy from the wind?
A.
Most of the air escapes through the space between the blades
B.
Some of the wind bounces back off the blades and is unable to pass through the machine
C.
The wind must be left with enough kinetic energy to exit the turbine
D.
The wind turbine has the same thermodynamic efficiency as a combustion engines
【单选题】What is the special feature of the Golden Rice?
A.
It can increase the vitamin A level in human body.
B.
It can easily be absorbed by young children.
C.
It is the byproduct of a gene conversion project.
D.
It can grow ripe weeks earlier than usual rice.
【简答题】to protect soil from wind and water
【单选题】Most memory researchers agree that our brains record—and remember at some level—everything that happens to us.
【单选题】The most commonly used locked level in implementing concurrency control is at which of the following levels? ( )
【单选题】The velocity of the apparent wind can be more than the true wind,and come from the same direction,if certain conditions are present.One condition is that the ______.
A.
Ship's speed must be less than the true wind velocity
B.
True wind must be from dead astern
C.
True wind velocity must be faster than the ship's speed
D.
True wind must be from dead ahead
【简答题】Most top-level managers increasingly recognize that participation in ______ gives them an opportunity to explain the ways of business to the public and helps them to manage crises.