对与系统并列运行的同步发电机，励磁调节的作用是
A. 保持机端电压恒定
B. 调节发电机发出的无功功率
C. 调节发电机机端电压和发电机发出的无功功率
D. 调节发电机发出的有功电流
What statements about assembly line are true?
A. It is determined by analyzing the steps necessary to produce each product component and the final product.
B. It starts with a bare chassis.
C. As the units move by, each worker along the line performs a complecated task.
D. It consists entirely of machines run by machines, with little or no human supervision.
Automatic assembly machines are ____________ only if they produce a high level of output.
列宁提出社会主义可能在一国或数国首先胜利的理论依据是（）
A. 资本主义必须灭亡
B. 帝国主义时代资本主义政治经济发展不平衡的规律
C. 资本主义国家无产阶级与资产阶级的规律
D. 生产关系必须适应生产力发展要求的规律
微信支付 
支付宝支付