When the author needed a post-office box, ______.
A. his name was put on a waiting list
B. he wrote the postmaster a note of appreciation
C. many people had applied for post-office boxes before him
D. he asked the postmaster to make one for him
查看答案
At first the author looked upon life as a process of getting. He formed this view of life probably because ______.
A. of most people
B. he was similar to most people in looks
C. of his early education
D. about the neighborhood
At first the author looked upon life as a process of getting. He formed this view of life probably because ______.
A. of most people
B. he was similar to most people in looks
C. of his early education
D. he was brought up to like most people
交流铁芯线圈的匝数固定，当电源频率不变时，则铁芯中主磁通的最大值基本上决定于（ ）。
A. 铁芯的磁导率
B. 电源电压
C. 线圈匝数
D. 线圈阻抗
某三相异步电动机额定运行时的转速为1440转/分钟，电源频率为50Hz，此时转子电流的频率为（ ）Hz。
A. 2
B. 50
C. 47
D. 3
微信支付 
支付宝支付