【单选题】鸽子每次啄绿色键就能得到食物,这属于行为训练中的( )。
【判断题】引发“五四”爱国运动的直接导火索是巴黎和会上中国的外交失败。
【单选题】What is one advantage of solar drip irrigation systems mentioned in the passage?
A.
They are more reliable.
B.
They have initial advantage.
C.
They don't break down from time to time.
D.
They are more economical over time.
【判断题】五四运动的直接导火索,是巴黎和会上中国外交的失败。
【单选题】According to the last paragraph, what can be concluded?
A.
Solar and wind energy systems cost a lot for producing electricity.
B.
People had better pay for the utility instead of producing electricity.
C.
Solar and wind energy can provide cheap and continuous electricity.
D.
Solar and wind energy is reasonable and cheap for remote villagers.
【单选题】Choose the word or phrase that is closest in meaning to the underlined part. NASA worked in the 1970s and early 1980s to research the possibilities of using Solar Power Satellite (SPS) systems with la...
A.
shed solar energy to the Earth’s surface from the satellite
B.
set the satellite down to the Earth’s surface with power
C.
shut down the power on the Earth’s surface from the satellite
D.
switch off power to the Earth’s surface from the satellite
【单选题】膜表面的流速增大,则浓度极化( ),截留率( )。